Method for evaluating hygroscopicity of energetic material under different temperature and humidity conditions

Abstract

The invention discloses a method for evaluating the hygroscopicity of an energetic material under different temperature and humidity conditions, which achieves the purpose of evaluating the hygroscopicity of various energetic molecules under any temperature and humidity conditions by establishing an energetic molecule model and controlling the size of a system model according to the water molecule density under various temperature and humidity conditions. And the influence of external environmental factors and human factors is avoided. The simulation method provided by the invention is simpler, safer and more efficient, the experiment needs longer time from sample preparation to hygroscopicity characterization, and the simulation method can simultaneously calculate the hygroscopicity of the sample under a plurality of different conditions, so that the time for evaluating the hygroscopicity of the energetic molecules is greatly saved.

Description

Technical Field

[0001] The invention relates to a method for evaluating the hygroscopicity of energetic materials under different temperature and humidity conditions, belonging to the field of energetic materials. Background Art

[0002] Energetic materials refer to materials that can release a large amount of chemical energy during chemical reactions. They are widely used in explosives (propellants, explosives, propellants, pyrotechnic agents, etc.). There are both theoretical and experimental studies on energetic materials. At present, the research focus of energetic materials is on improving their energy density, stability, safety and environmental protection. In terms of stability research, the hygroscopicity of materials is crucial to the evaluation of the stability of energetic materials. It is the key to the long-term storage of energetic materials without performance degradation, maintaining good processing performance, and safe and stable energy release, which directly affects the actual application performance of explosives.

[0003] Therefore, it is of great significance to evaluate the hygroscopicity of energetic materials. Usually, the hygroscopicity evaluation method of energetic materials is carried out through experimental operations, such as the dryer balance method (GJB 770B-2005, Method 404.1 Hygroscopicity dryer balance method [S] of gunpowder test method) and the dynamic adsorption method (WJ 20699-2018, Dynamic adsorption method of hygroscopicity of energetic materials for pyrotechnic performance test [S] of gunpowder). The dryer balance method mainly places the pre-dried and weighed sample in a dryer, adds a saturated solution of a specific salt into the dryer, and places the dryer containing the sample at a certain temperature to create a certain temperature and humidity environment. By weighing the sample before and after moisture absorption and testing the change in sample mass over a certain period of time, the hygroscopicity of the sample is evaluated. Similarly, the dynamic adsorption method also obtains the hygroscopicity evaluation of the sample through experimental methods, specifically, passing air of a certain temperature and humidity through a sample of a certain mass, and obtaining the moisture absorption rate value of the sample according to the change in the mass of the sample. Both of these standards for evaluating hygroscopicity are experimental methods. The repeatability of each experiment is greatly affected by environmental and human factors. The consideration of the hygroscopic properties of the sample can only provide a limited reference. In addition, the preparation of samples is required for testing, which takes a lot of time. In addition to the above-mentioned weighing method, foreign studies on hygroscopicity also make extensive use of microscopic characterization methods such as X-rays and scanning electron microscopes to analyze the hygroscopicity of samples from a more microscopic perspective. For example, Alexei V. Tivanski et al. (Suman Ghorai, Alexei V. Tivanski. Hygroscopic Behavior of Individual Submicrometer Particles Studied by X-ray Spectromicroscopy [J]. Analytical Chemistry, 2010, 82 (22), 9289–9298.) from the United States used X-ray spectromicroscopy to study the hygroscopic behavior of individual submicron particles and proposed a new application of single-particle scanning transmission X-ray microscopy and near edge X-ray absorption fine structure spectroscopy for quantitative analysis of the hygroscopic properties and phase transitions of individual submicron particles. This method exposes the deposited individual particles to water vapor at different relative humidity and then performs STXM / NEXAFS spectromicroscopy analysis, which can provide quantitative information on the physical and chemical properties of the particles and how these properties change with relative humidity.Martin Ebert et al. from Germany (Martin Ebert, Marion Inerle-Hof, Stephan Weinbruch. Environmental scanning electron microscopy as a new technique to determine the hygroscopic behavior of individual aerosol particles [J]. Atmospheric Environment, 2002, 36 (39–40), 5909–5916.) used environmental scanning electron microscopy (ESEM) to study the hygroscopic behavior of particles in the range of 0.1 to 20 mm. This technique allows in situ observation of individual aerosol particles while changing the temperature and / or relative humidity of the sample chamber. The hygroscopic behavior of these particles (e.g., deliquescence, adsorption of water on the particle surface) can be directly observed with a lateral resolution of 8-15 nanometers. The authors believe that the values ​​obtained by ESEM are in good agreement with those found in the literature.

[0004] In summary, most of these evaluations of hygroscopicity are experimental studies. However, there are certain errors in the control of ambient temperature / humidity, so the experimental data will fluctuate. At present, there is no suitable model and method to better compare the hygroscopicity of energetic materials under different temperature and humidity conditions. If this method and technology can be broken through, it will greatly facilitate the research on the anti-hygroscopicity of energetic materials, and it can also provide new theoretical guidance for us to test / evaluate the hygroscopicity of energetic materials. Summary of the invention

[0005] In view of the fact that the strong hygroscopicity of energetic materials affects the long-term storage, efficient utilization and safety of the materials, the purpose of the present invention is to provide a simple and efficient method for evaluating the hygroscopicity of energetic materials under different temperature and humidity environments.

[0006] The technical solution to realize the present invention is: the present invention provides a method for evaluating the hygroscopicity of energetic materials under different temperature and humidity conditions, which specifically includes the following steps:

[0007] The first step is to import the standard cif file of the initial unit cell of energetic molecules into the Materials Studio molecular simulation software, construct energetic molecular clusters of a certain size, and place the constructed energetic molecular clusters in a larger cubic grid. Water molecules with a known density under specific temperature and relative humidity conditions multiplied by n are filled into the space between the energetic molecular clusters and the cubic grid to construct the initial model.

[0008] The second step is to perform NVT molecular dynamics calculation on the constructed initial model, take out the last frame model after the molecular dynamics calculation, and use the Forcite module to perform structural optimization of the non-optimized unit cell to eliminate the structural instability factors in the structure, and obtain the stable model M after moisture absorption;

[0009] The third step is to decompose the stable model M after moisture absorption, and extract the model M1 of the single water molecule after moisture absorption and the model M2 of the single energetic molecular cluster. Use the Forcite module to calculate the system energy of these three models, that is, the energy E of M1 water 、Energy of M2 cluster 、Energy of M total Finally, the interaction energy E between the energetic molecular cluster and water molecules under specific temperature and relative humidity conditions is obtained. interaction The hygroscopicity of the energetic molecular clusters was evaluated by the interaction energy between the energetic molecular clusters and water molecules under different temperature and relative humidity conditions.

[0010] Preferably, in the first step, the energetic molecules include but are not limited to any energetic hygroscopic materials such as oxidants, explosives, metal powders, and hydrogen storage materials. The oxidants may be ammonium perchlorate (AP), potassium perchlorate (KP), ammonium dinitramide (ADN), ammonium nitrate (AN), and the like, as well as their eutectics, mixed crystals, and modified crystals; the explosives may be hexanitrohexaazaisowurtane (CL-20), 1'1-dihydroxy-5,5'-bipentadienyldihydroxyamine (TKX-50), 3,4-dinitrofuroxan (DNTF), All-nitrogen / multi-nitrogen energetic materials, and their eutectics, mixed crystals and modified crystals; metal powders can be aluminum powder (Al), boron powder (B), magnesium powder (Mg) or their alloy powders, etc.; hydrogen storage materials can be magnesium hydride (MgH2), aluminum hydride (AlH3), lithium aluminum hydride (LiAlH4), magnesium aluminum hydride (Mg(AlH4)2), etc. It is worth noting that this method is also applicable to non-energetic materials; the morphology of energetic molecular clusters can be spheres, cubes, various cylinders, various cones and other three-dimensional figures, and energetic molecular clusters of a certain size (longest side / diameter) can be In a larger cubic grid, the side length of the grid is

[0011] Preferably, in the first step, the specific temperature and relative humidity conditions refer to a temperature of 0 to 100° C. and a relative humidity of 0% to 100%.

[0012] Preferably, in the first step, the water molecules with known density under specific temperature and relative humidity conditions are multiplied by n times so that the density of the water molecules is ≥ 0.0001 g / cm 3Meet the modeling requirements of Materials studio molecular simulation software.

[0013] Preferably, in the second step, when performing NVT molecular dynamics calculations, the dynamic parameters are set, including: the time is set to 20ps to 1000ps, the temperature control method adopts the Nose method, the calculation accuracy of the structure optimization is greater than or equal to the default Middle accuracy of the Forcite module, and the displacement factor (Displacement) needs to be considered.

[0014] Preferably, in the third step, E is determined according to the formula interaction =E total -E water -E cluster .

[0015] Preferably, in the third step, the calculation accuracy of the energy is greater than or equal to the default Middle accuracy of the Forcite module of the Materials studio software.

[0016] Preferably, in the third step, the interaction energy E of the energetic molecular clusters with water molecules under different temperature and relative humidity conditions is interaction , the hygroscopicity of the energetic molecular clusters was evaluated, E interaction The larger the absolute value of is, the stronger the hygroscopicity of the energetic molecular clusters is.

[0017] The method for evaluating the hygroscopicity of energetic materials under different temperature and humidity conditions proposed by the present invention has the following advantages compared with the prior art methods:

[0018] (1) The present invention establishes an energetic molecule model based on the density of water molecules under various temperature and humidity conditions and controls the size of the system model, thereby achieving the purpose of evaluating the hygroscopic properties of various energetic molecules under arbitrary temperature and humidity conditions (temperature: 0-100°C, relative humidity 0%-100%), and is not affected by external environmental factors and human factors.

[0019] (2) The simulation method proposed in the present invention is simpler, safer and more efficient. The experiment takes a long time from sample preparation to hygroscopicity characterization, while the simulation method can simultaneously calculate the hygroscopicity of samples under multiple different conditions, greatly saving the time for evaluating the hygroscopicity of energetic molecules.

[0020] (3) The present invention is helpful to accelerate the development and application of new energetic materials in the evaluation of hygroscopicity of energetic materials. The hygroscopicity results of energetic materials can be obtained without conducting experiments, which is of great significance for the optimization of energetic materials and is also applicable to the evaluation of various modified energetic materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the unit cell of the ADN crystal in Example 1.

[0022] Figure 2 is the radius in Example 1 The ADN spherical clusters are placed on the Model in a cubic grid.

[0023] Figure 3 In Example 1, the density of the filled 3 The model after the water molecule.

[0024] Figure 4 This is the post-moisture absorption model obtained by performing NVT molecular dynamics for 100 ps in Example 1.

[0025] Figure 5 This is the stable ADN hygroscopic model after structural optimization in Example 1.

[0026] Figure 6 It is the molecular energy model of the three systems calculated in Example 1.

[0027] Figure 7 It is a schematic diagram of the principle of the method for evaluating the hygroscopicity of energetic materials under different temperature and humidity conditions described in the present invention. DETAILED DESCRIPTION

[0028] In order to further describe the present invention, the following examples are listed, but the present invention is not limited to the examples.

[0029] For the modification of many hygroscopic energetic materials, we hope to evaluate the hygroscopicity of the modified materials we designed in advance, select the best scheme from a large number of modification schemes, and then conduct experiments to verify, so as to greatly reduce the cost and time of the experiment and improve the accuracy of the experiment. Therefore, we proposed a theoretical simulation method to study the hygroscopicity of energetic material particles. The advantage of the theoretical method over the actual test is that the temperature and humidity of the external environment can be strictly applied as required, and the morphology, particle size and density of each experimental sample model can be controlled to be exactly the same, and there will be no large errors in the experimental data due to differences in environmental conditions and the sample itself.

[0030] Taking ADN as an example, the present invention provides a method for evaluating the hygroscopicity of energetic materials under different temperature and humidity conditions, and its principle schematic diagram is shown in FIG7 .

[0031] Implementation Example 1:

[0032] Step 1: According to the table of saturated vapor pressure of water molecules at different temperatures in books such as chemical manuals or chemical principles, the density of water molecules under standard atmospheric pressure, 40°C, and saturated humidity (100%) is obtained. The density of water molecules under standard atmospheric pressure, 40°C, and 10% relative humidity is calculated to be about 5.114×10 -6 g / cm 3 .

[0033] Step 2: Import the cif file of ammonium dinitramide (ADN) crystal into Materials Studio 2019 simulation software, and perform complete structural optimization on the initial unit cell of ADN to make the architecture more reasonable ( Figure 1 ), the calculation accuracy of the structure optimization is set to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to Then construct the radius ADN spherical nanoclusters and place the constructed ADN nanoclusters on a side length The body center position of the cube lattice ( Figure 2 ), the water molecule density calculated in the previous step is 5.114×10 -6 g / cm 3 Multiply by 200 to get 0.00102 g / cm 3 (Because the calculated water molecule density value is too small in actual situation, and the minimum density of molecules added by the Amorphous module of Materialsstudio 2019 simulation software is 0.0001g / cm 3 Therefore, when adding water molecules, the water molecule density under all temperature and humidity systems is multiplied by n times so that the minimum density of the added water molecules is not less than 0.0001g / cm 3 , so as to achieve the purpose of studying the hygroscopic effect of energetic molecules on water molecules under different temperature and humidity conditions, and to meet the requirements of modeling accuracy of simulation software), filling the gaps between ADN clusters and cubic lattices with water molecules of this density ( Figure 3 ), and the initial moisture absorption model of ADN was obtained.

[0034] Step 3: Use the Forcite module of Materials studio simulation software to perform molecular dynamics simulation of NVT on the constructed AND initial moisture absorption model. The molecular dynamics time is set to 100ps. Finally, the last frame model after the molecular dynamics calculation is taken out ( Figure 4), and use the Forcite module to perform structural optimization operations without optimizing the unit cell to eliminate unstable factors such as stress in the structure, and obtain a stable model after moisture absorption ( Figure 5 ), the calculation accuracy of the structure optimization is set to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to

[0035] Step 4: Use the atom selection function to split the above stable model of ADN after moisture absorption, separate the model of single water molecules after moisture absorption and the model of single energetic molecular clusters, and use the Forcite module to calculate the system energy of these three models ( Figure 6 ), in order: E water =-216.135 kcal / mol,E cluster =-82579.033 kcal / mol,E total =-84334.082 kcal / mol. Finally, the energy of the complete system after moisture absorption minus the energy of the individual energetic molecular cluster and then minus the energy of the individual water molecule is used to obtain the water molecule interaction energy of the ADN spherical cluster at 40°C and 10% relative humidity: E interaction =E total -E water -E cluster =-1538.914 kcal / mol.

[0036] Implementation Example 2:

[0037] Step 1: Calculate the water molecule density under standard atmospheric pressure, 40°C, and 20% relative humidity to be approximately 1.023×10 -5 g / cm 3 .

[0038] Step 2: Import the cif file of the ADN crystal into the Materials Studio 2019 simulation software, perform a complete structural optimization on the ADN initial unit cell to make the system architecture more reasonable, and set the calculation accuracy of the structural optimization to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to Then construct the radius ADN spherical nanoclusters and place the constructed ADN nanoclusters on a side length The water molecule density 1.023×10 -5 g / cm 3 Multiply by 200 to get 0.00205 g / cm 3 (≥0.0001g / cm 3 The density of water molecules is filled into the gaps between the ADN clusters and the cubic lattice (which meets the modeling requirements of the software).

[0039] Step 3: The constructed ADN moisture absorption model was simulated by molecular dynamics simulation of NVT using the Forcite module of Materials studio simulation software. The molecular dynamics time was set to 100ps. Finally, the last frame model after the molecular dynamics calculation was taken out and the Forcite module was used to perform structural optimization operations without optimizing the unit cell to eliminate the unstable factors such as stress in the structure, and obtain a stable model after moisture absorption. The calculation accuracy of the structural optimization was set to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to

[0040] Step 4: Use the atom selection function to split the above stable model of ADN after moisture absorption, and separate the model of single water molecules after moisture absorption, the model of single energetic molecular clusters, and the moisture absorption model of the complete system. Use the Forcite module to calculate the system energy of these three separation models, which are: E water =-695.632 kcal / mol,E cluster =-82416.823 kcal / mol,E total =-85538.839 kcal / mol. Finally, the energy of the complete system after moisture absorption minus the energy of the individual energetic molecular cluster and then minus the energy of the individual water molecule is used to obtain the water molecule interaction energy of the ADN spherical cluster at 40°C and 20% relative humidity: E interaction =E total -E water -E cluster =-2426.384 kcal / mol.

[0041] Implementation Example 3:

[0042] Step 1: Calculate the water molecule density under standard atmospheric pressure, 40°C, and 30% relative humidity to be approximately 1.534×10 -5 g / cm 3 .

[0043] Step 2: Import the cif file of the ADN crystal into the Materials Studio 2019 simulation software, perform a complete structural optimization on the ADN initial unit cell to make the system architecture more reasonable, and set the calculation accuracy of the structural optimization to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to Then construct the radius ADN spherical nanoclusters and place the constructed ADN nanoclusters on a side length The water molecule density 1.534×10 -5 g / cm 3 Multiply by 200 to get 0.00307 g / cm 3 (≥0.0001g / cm 3 The density of water molecules is filled into the gaps between the ADN clusters and the cubic lattice (which meets the modeling requirements of the software).

[0044] Step 3: The constructed ADN moisture absorption model was simulated by molecular dynamics simulation of NVT using the Forcite module of Materials studio simulation software. The molecular dynamics time was set to 100ps. Finally, the last frame model after the molecular dynamics calculation was taken out and the Forcite module was used to perform structural optimization operations without optimizing the unit cell to eliminate the unstable factors such as stress in the structure, and obtain a stable model after moisture absorption. The calculation accuracy of the structural optimization was set to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to

[0045] Step 4: Use the atom selection function to split the above stable model of ADN after moisture absorption, and separate the model of single water molecules after moisture absorption, the model of single energetic molecular clusters, and the moisture absorption model of the complete system. Use the Forcite module to calculate the system energy of these three separation models, which are: E water =-1288.881 kcal / mol,E cluster =-82295.940 kcal / mol,E total=-86443.139 kcal / mol. Finally, the energy of the complete system after moisture absorption minus the energy of the individual energetic molecular cluster and then minus the energy of the individual water molecule is used to obtain the water molecule interaction energy of the ADN spherical cluster at 40°C and 30% relative humidity: E interaction =E total -E water -E cluster =-2858.318 kcal / mol.

[0046] Implementation Example 4:

[0047] Step 1: Calculate the water molecule density under standard atmospheric pressure, 40°C, and 40% relative humidity to be approximately 2.046×10 -5 g / cm 3 .

[0048] Step 2: Import the cif file of the ADN crystal into the Materials Studio 2019 simulation software, perform a complete structural optimization on the ADN initial unit cell to make the system architecture more reasonable, and set the calculation accuracy of the structural optimization to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to Then construct the radius ADN spherical nanoclusters and place the constructed ADN nanoclusters on a side length The water molecule density 2.046×10 -5 g / cm 3 Multiply by 200 to get 0.00409 g / cm 3 (≥0.0001g / cm 3 The density of water molecules is filled into the gaps between the ADN clusters and the cubic lattice (which meets the modeling requirements of the software).

[0049] Step 3: The constructed ADN moisture absorption model was simulated by molecular dynamics simulation of NVT using the Forcite module of Materials studio simulation software. The molecular dynamics time was set to 100ps. Finally, the last frame model after the molecular dynamics calculation was taken out and the Forcite module was used to perform structural optimization operations without optimizing the unit cell to eliminate the unstable factors such as stress in the structure, and obtain a stable model after moisture absorption. The calculation accuracy of the structural optimization was set to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to

[0050] Step 4: Use the atom selection function to split the above stable model of ADN after moisture absorption, and separate the model of single water molecules after moisture absorption, the model of single energetic molecular clusters, and the moisture absorption model of the complete system. Use the Forcite module to calculate the system energy of these three separation models, which are: E water =-1906.746 kcal / mol,E cluster =-81905.513 kcal / mol,E total =-87476.106 kcal / mol. Finally, the energy of the complete system after moisture absorption minus the energy of the individual energetic molecular cluster and then minus the energy of the individual water molecule is used to obtain the water molecule interaction energy of the ADN spherical cluster at 40°C and 40% relative humidity: E interaction =E total -E water -E cluster =-3663.847 kcal / mol.

[0051] Implementation Example 5:

[0052] Step 1: Calculate the water molecule density under standard atmospheric pressure, 40°C, and 50% relative humidity to be approximately 2.557×10 -5 g / cm 3 .

[0053] Step 2: Import the cif file of the ADN crystal into the Materials Studio 2019 simulation software, perform a complete structural optimization on the ADN initial unit cell to make the system architecture more reasonable, and set the calculation accuracy of the structural optimization to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to Then construct the radius ADN spherical nanoclusters and place the constructed ADN nanoclusters on a side length The water molecule density 2.557×10 -5 g / cm 3 Multiply by 200 to get 0.00511 g / cm 3 (≥0.0001g / cm 3 The density of water molecules is filled into the gaps between the ADN clusters and the cubic lattice (which meets the modeling requirements of the software).

[0054] Step 3: The constructed ADN moisture absorption model was simulated by molecular dynamics simulation of NVT using the Forcite module of Materials studio simulation software. The molecular dynamics time was set to 100ps. Finally, the last frame model after the molecular dynamics calculation was taken out and the Forcite module was used to perform structural optimization operations without optimizing the unit cell to eliminate the unstable factors such as stress in the structure, and obtain a stable model after moisture absorption. The calculation accuracy of the structural optimization was set to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to

[0055] Step 4: Use the atom selection function to split the above stable model of ADN after moisture absorption, and separate the model of single water molecules after moisture absorption, the model of single energetic molecular clusters, and the moisture absorption model of the complete system. Use the Forcite module to calculate the system energy of these three separation models, which are: E water =-2701.862 kcal / mol,E cluster =-81576.847 kcal / mol,E total =-88930.299 kcal / mol. Finally, the energy of the complete system after moisture absorption minus the energy of the individual energetic molecular cluster and then minus the energy of the individual water molecule is used to obtain the water molecule interaction energy of the ADN spherical cluster at 40°C and 50% relative humidity: E interaction =E total -E water -E cluster =-4651.590 kcal / mol.

[0056] Implementation Example 6:

[0057] Step 1: Calculate the water molecule density under standard atmospheric pressure, 40°C, and 60% relative humidity to be approximately 3.068×10 -5 g / cm 3 .

[0058] Step 2: Import the cif file of the ADN crystal into the Materials Studio 2019 simulation software, perform a complete structural optimization on the ADN initial unit cell to make the system architecture more reasonable, and set the calculation accuracy of the structural optimization to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to Then construct the radius ADN spherical nanoclusters and place the constructed ADN nanoclusters on a side length The water molecule density 3.068×10 -5 g / cm 3 Multiply by 200 to get 0.00614 g / cm 3 (≥0.0001g / cm 3 The density of water molecules is filled into the gaps between the ADN clusters and the cubic lattice (which meets the modeling requirements of the software).

[0059] Step 3: The constructed ADN moisture absorption model was simulated by molecular dynamics simulation of NVT using the Forcite module of Materials studio simulation software. The molecular dynamics time was set to 100ps. Finally, the last frame model after the molecular dynamics calculation was taken out and the Forcite module was used to perform structural optimization operations without optimizing the unit cell to eliminate the unstable factors such as stress in the structure, and obtain a stable model after moisture absorption. The calculation accuracy of the structural optimization was set to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to

[0060] Step 4: Use the atom selection function to split the above stable model of ADN after moisture absorption, and separate the model of single water molecules after moisture absorption, the model of single energetic molecular clusters, and the moisture absorption model of the complete system. Use the Forcite module to calculate the system energy of these three separation models, which are: E water =-3568.760 kcal / mol, E cluster =-81556.012 kcal / mol,E total =-89888.618 kcal / mol. Finally, the energy of the complete system after moisture absorption minus the energy of the individual energetic molecular cluster and then minus the energy of the individual water molecule is used to obtain the water molecule interaction energy of the ADN spherical cluster at 40°C and 60% relative humidity: E interaction =E total -E water -E cluster =-4763.846 kcal / mol.

[0061] Implementation Example 7:

[0062] Step 1: Calculate the water molecule density under standard atmospheric pressure, 40°C, and 70% relative humidity to be approximately 3.580×10 -5 g / cm 3 .

[0063] Step 2: Import the cif file of the ADN crystal into the Materials Studio 2019 simulation software, perform a complete structural optimization on the ADN initial unit cell to make the system architecture more reasonable, and set the calculation accuracy of the structural optimization to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to Then construct the radius ADN spherical nanoclusters and place the constructed ADN nanoclusters on a side length The water molecule density 3.580×10 -5 g / cm 3 Multiply by 200 to get 0.00716 g / cm 3 (≥0.0001g / cm 3 The density of water molecules is filled into the gaps between the ADN clusters and the cubic lattice (which meets the modeling requirements of the software).

[0064] Step 3: The constructed ADN moisture absorption model was simulated by molecular dynamics simulation of NVT using the Forcite module of Materials studio simulation software. The molecular dynamics time was set to 100ps. Finally, the last frame model after the molecular dynamics calculation was taken out and the Forcite module was used to perform structural optimization operations without optimizing the unit cell to eliminate the unstable factors such as stress in the structure, and obtain a stable model after moisture absorption. The calculation accuracy of the structural optimization was set to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to

[0065] Step 4: Use the atom selection function to split the above stable model of ADN after moisture absorption, and separate the model of single water molecules after moisture absorption, the model of single energetic molecular clusters, and the moisture absorption model of the complete system. Use the Forcite module to calculate the system energy of these three separation models, which are: E water =-4267.819 kcal / mol,E cluster=-81167.758 kcal / mol,E total =-90816.034 kcal / mol. Finally, the energy of the complete system after moisture absorption minus the energy of the individual energetic molecular cluster and then minus the energy of the individual water molecule is used to obtain the water molecule interaction energy of the ADN spherical cluster at 40°C and 70% relative humidity: E interaction =E total -E water -E cluster =-5380.457 kcal / mol.

[0066] Implementation Example 8:

[0067] Step 1: Calculate the water molecule density under standard atmospheric pressure, 40°C, and 80% relative humidity to be approximately 4.091×10 -5 g / cm 3 .

[0068] Step 2: Import the cif file of the ADN crystal into the Materials Studio 2019 simulation software, perform a complete structural optimization on the ADN initial unit cell to make the system architecture more reasonable, and set the calculation accuracy of the structural optimization to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to Then construct the radius ADN spherical nanoclusters and place the constructed ADN nanoclusters on a side length The water molecule density 4.091×10 -5 g / cm 3 Multiply by 200 to get 0.00818 g / cm 3 (≥0.0001g / cm 3 The density of water molecules is filled into the gaps between the ADN clusters and the cubic lattice (which meets the modeling requirements of the software).

[0069] Step 3: The constructed ADN moisture absorption model was simulated by molecular dynamics simulation of NVT using the Forcite module of Materials studio simulation software. The molecular dynamics time was set to 100ps. Finally, the last frame model after the molecular dynamics calculation was taken out and the Forcite module was used to perform structural optimization operations without optimizing the unit cell to eliminate the unstable factors such as stress in the structure, and obtain a stable model after moisture absorption. The calculation accuracy of the structural optimization was set to Ultra-fine (Energy: 2×10-5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to

[0070] Step 4: Use the atom selection function to split the above stable model of ADN after moisture absorption, and separate the model of single water molecules after moisture absorption, the model of single energetic molecular clusters, and the moisture absorption model of the complete system. Use the Forcite module to calculate the system energy of these three separation models, which are: E water =-5445.833 kcal / mol,E cluster =-81311.527 kcal / mol,E total =-92178.651 kcal / mol. Finally, the energy of the complete system after moisture absorption minus the energy of the individual energetic molecular cluster and then minus the energy of the individual water molecule is used to obtain the water molecule interaction energy of the ADN spherical cluster at 40°C and 80% relative humidity: E interaction =E total -E water -E cluster =-5421.291 kcal / mol.

[0071] Implementation Example 9:

[0072] Step 1: Calculate the water molecule density under standard atmospheric pressure, 40°C, and 90% relative humidity to be approximately 4.603×10 -5 g / cm 3 .

[0073] Step 2: Import the cif file of the ADN crystal into the Materials Studio 2019 simulation software, perform a complete structural optimization on the ADN initial unit cell to make the system architecture more reasonable, and set the calculation accuracy of the structural optimization to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to Then construct the radius ADN spherical nanoclusters and place the constructed ADN nanoclusters on a side length The water molecule density calculated in the previous step is 4.603×10 -5 g / cm 3 Multiply by 200 to get 0.00921 g / cm 3 (≥0.0001g / cm 3The density of water molecules is filled into the gaps between the ADN clusters and the cubic lattice (which meets the modeling requirements of the software).

[0074] Step 3: The constructed ADN moisture absorption model was simulated by molecular dynamics simulation of NVT using the Forcite module of Materials studio simulation software. The molecular dynamics time was set to 100ps. Finally, the last frame model after the molecular dynamics calculation was taken out and the Forcite module was used to perform structural optimization operations without optimizing the unit cell to eliminate the unstable factors such as stress in the structure, and obtain a stable model after moisture absorption. The calculation accuracy of the structural optimization was set to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to

[0075] Step 4: Use the atom selection function to split the above stable model of ADN after moisture absorption, and separate the model of single water molecules after moisture absorption, the model of single energetic molecular clusters, and the moisture absorption model of the complete system. Use the Forcite module to calculate the system energy of these three separation models, which are: E water =-6279.108 kcal / mol,E cluster =-81009.285 kcal / mol,E total = -93275.496 kcal / mol. Finally, the energy of the complete system after moisture absorption minus the energy of the individual energetic molecular cluster and then minus the energy of the individual water molecule is used to obtain the water molecule interaction energy of the ADN spherical cluster at 40°C and 90% relative humidity: E interaction =E total -E water -E cluster =-5987.103 kcal / mol.

[0076] Implementation Example 10:

[0077] Step 1: Calculate the water molecule density under standard atmospheric pressure, 40°C, and 100% relative humidity to be approximately 5.114×10 -5 g / cm 3 .

[0078] Step 2: Import the cif file of the ADN crystal into the Materials Studio 2019 simulation software, perform a complete structural optimization on the ADN initial unit cell to make the system architecture more reasonable, and set the calculation accuracy of the structural optimization to Ultra-fine (Energy: 2×10-5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to Then construct the radius ADN spherical nanoclusters and place the constructed ADN nanoclusters on a side length The water molecule density 5.114×10 -5 g / cm 3 Multiply by 200 to get 0.01023 g / cm 3 (≥0.0001g / cm 3 The density of water molecules is filled into the gaps between the ADN clusters and the cubic lattice (which meets the modeling requirements of the software).

[0079] Step 3: The constructed ADN moisture absorption model was simulated by molecular dynamics simulation of NVT using the Forcite module of Materials studio simulation software. The molecular dynamics time was set to 100ps. Finally, the last frame model after the molecular dynamics calculation was taken out and the Forcite module was used to perform structural optimization operations without optimizing the unit cell to eliminate the unstable factors such as stress in the structure, and obtain a stable model after moisture absorption. The calculation accuracy of the structural optimization was set to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to

[0080] Step 4: Use the atom selection function to split the above stable model of ADN after moisture absorption, and separate the model of single water molecules after moisture absorption, the model of single energetic molecular clusters, and the moisture absorption model of the complete system. Use the Forcite module to calculate the system energy of these three separation models, which are: E water =-7159.297 kcal / mol,E cluster =-80812.573 kcal / mol,E total =-94517.628 kcal / mol. Finally, the energy of the complete system after moisture absorption minus the energy of the individual energetic molecular cluster and then minus the energy of the individual water molecule is used to obtain the water molecule interaction energy of the ADN spherical cluster at 40°C and 100% relative humidity: E interaction =E total -E water -E cluster =-6545.758 kcal / mol.

[0081] Implementation Example 11:

[0082] Step 1: Calculate the water molecule density under standard atmospheric pressure, 0°C, and 40% relative humidity to be approximately 1.936×10 -6 g / cm 3 .

[0083] Step 2: Import the cif file of the ADN crystal into the Materials Studio 2019 simulation software, perform a complete structural optimization on the ADN initial unit cell to make the system architecture more reasonable, and set the calculation accuracy of the structural optimization to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to Then construct the radius ADN spherical nanoclusters and place the constructed ADN nanoclusters on a side length The water molecule density 1.936×10 -6 g / cm 3 Multiply by 200 to get 0.00039 g / cm 3 (≥0.0001g / cm 3 The density of water molecules is filled into the gaps between the ADN clusters and the cubic lattice (which meets the modeling requirements of the software).

[0084] Step 3: The constructed ADN moisture absorption model was simulated by molecular dynamics simulation of NVT using the Forcite module of Materials studio simulation software. The molecular dynamics time was set to 100ps. Finally, the last frame model after the molecular dynamics calculation was taken out and the Forcite module was used to perform structural optimization operations without optimizing the unit cell to eliminate the unstable factors such as stress in the structure, and obtain a stable model after moisture absorption. The calculation accuracy of the structural optimization was set to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to

[0085] Step 4: Use the atom selection function to split the above stable model of ADN after moisture absorption, and separate the model of single water molecules after moisture absorption, the model of single energetic molecular clusters, and the moisture absorption model of the complete system. Use the Forcite module to calculate the system energy of these three separation models, which are: E water=-58.448 kcal / mol,E cluster =-82935.859 kcal / mol,E total =-83683.110 kcal / mol. Finally, the energy of the complete system after moisture absorption minus the energy of the individual energetic molecular cluster and then minus the energy of the individual water molecule is used to obtain the water molecule interaction energy of the ADN spherical cluster at 0°C and 40% relative humidity: E interaction =E total -E water -E cluster =-688.803 kcal / mol.

[0086] Implementation Example 12:

[0087] Step 1: Calculate the water molecule density under standard atmospheric pressure, 20°C, and 40% relative humidity to be approximately 6.876×10 -6 g / cm 3 .

[0088] Step 2: Import the cif file of the ADN crystal into the Materials Studio 2019 simulation software, perform a complete structural optimization on the ADN initial unit cell to make the system architecture more reasonable, and set the calculation accuracy of the structural optimization to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to Then construct the radius ADN spherical nanoclusters and place the constructed ADN nanoclusters on a side length The water molecule density calculated in the previous step is 6.876×10 -6 g / cm 3 Multiply by 200 to get 0.00138 g / cm 3 (≥0.0001g / cm 3 The density of water molecules is filled into the gaps between the ADN clusters and the cubic lattice (which meets the modeling requirements of the software).

[0089] Step 3: The constructed ADN moisture absorption model was simulated by molecular dynamics simulation of NVT using the Forcite module of Materials studio simulation software. The molecular dynamics time was set to 100ps. Finally, the last frame model after the molecular dynamics calculation was taken out and the Forcite module was used to perform structural optimization operations without optimizing the unit cell to eliminate the unstable factors such as stress in the structure, and obtain a stable model after moisture absorption. The calculation accuracy of the structural optimization was set to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to

[0090] Step 4: Use the atom selection function to split the above stable model of ADN after moisture absorption, and separate the model of single water molecules after moisture absorption, the model of single energetic molecular clusters, and the moisture absorption model of the complete system. Use the Forcite module to calculate the system energy of these three separation models, which are: E water =-437.215 kcal / mol,E cluster =-82665.744 kcal / mol,E total =-84726.504 kcal / mol. Finally, the energy of the complete system after moisture absorption minus the energy of the individual energetic molecular cluster and then minus the energy of the individual water molecule is used to obtain the water molecule interaction energy of the ADN spherical cluster at 20°C and 40% relative humidity: E interaction =E total -E water -E cluster =-1623.545 kcal / mol.

[0091] Implementation Example 13:

[0092] Step 1: Calculate the water molecule density under standard atmospheric pressure, 60°C, and 40% relative humidity to be approximately 5.204×10 -5 g / cm 3 .

[0093] Step 2: Import the cif file of the ADN crystal into the Materials Studio 2019 simulation software, perform a complete structural optimization on the ADN initial unit cell to make the system architecture more reasonable, and set the calculation accuracy of the structural optimization to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to Then construct the radius ADN spherical nanoclusters and place the constructed ADN nanoclusters on a side length The water molecule density 5.204×10 -5 g / cm 3 Multiply by 200 to get 0.01041 g / cm 3 (≥0.0001g / cm 3 The density of water molecules is filled into the gaps between the ADN clusters and the cubic lattice (which meets the modeling requirements of the software).

[0094] Step 3: The constructed ADN moisture absorption model was simulated by molecular dynamics simulation of NVT using the Forcite module of Materials studio simulation software. The molecular dynamics time was set to 100ps. Finally, the last frame model after the molecular dynamics calculation was taken out and the Forcite module was used to perform structural optimization operations without optimizing the unit cell to eliminate the unstable factors such as stress in the structure, and obtain a stable model after moisture absorption. The calculation accuracy of the structural optimization was set to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to

[0095] Step 4: Use the atom selection function to split the above stable model of ADN after moisture absorption, and separate the model of single water molecules after moisture absorption, the model of single energetic molecular clusters, and the moisture absorption model of the complete system. Use the Forcite module to calculate the system energy of these three separation models, which are: E water =-6939.613 kcal / mol,E cluster =-80771.684 kcal / mol,E total = -94104.408 kcal / mol. Finally, the energy of the complete system after moisture absorption minus the energy of the individual energetic molecular cluster and then minus the energy of the individual water molecule is used to obtain the water molecule interaction energy of the ADN spherical cluster at 60°C and 40% relative humidity: E interaction =E total -E water -E cluster =-6393.111 kcal / mol.

[0096] Implementation Example 14:

[0097] Step 1: Calculate the water molecule density under standard atmospheric pressure, 40°C, and 80% relative humidity to be approximately 4.091×10 -5 g / cm 3 .

[0098] Step 2: Import the cif file of ammonium nitrate (AN) crystal into Materials Studio 2019 simulation software, perform complete structural optimization on the initial unit cell of AN to make the system structure more reasonable, and set the calculation accuracy of structural optimization to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to Then construct the radius The constructed AN nanoclusters are placed on the side length The water molecule density 4.091×10 -5 g / cm 3 Multiply by 200 to get 0.00818 g / cm 3 (≥0.0001g / cm 3 In line with the software modeling requirements), water molecules of this density are filled into the gaps between the AN clusters and the cubic lattice.

[0099] Step 3: The constructed AN moisture absorption model was simulated by molecular dynamics simulation of NVT using the Forcite module of Materials studio simulation software. The molecular dynamics time was set to 100ps. Finally, the last frame model after the molecular dynamics calculation was taken out, and the Forcite module was used to perform structural optimization operations without optimizing the unit cell to eliminate the unstable factors such as stress in the structure, and obtain a stable model after moisture absorption. The calculation accuracy of the structural optimization was set to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to

[0100] Step 4: Use the atom selection function to split the above stable model of AN after moisture absorption, and separate the model of single water molecules after moisture absorption, the model of single energetic molecular clusters, and the moisture absorption model of the complete system. Use the Forcite module to calculate the system energy of these three separation models, which are: E water =-2226.375 kcal / mol,E cluster=-73165.193 kcal / mol,E total =-80708.985 kcal / mol. Finally, the energy of the complete system after moisture absorption minus the energy of the individual energetic molecular cluster and then minus the energy of the individual water molecule is used to obtain the water molecule interaction energy of the AN spherical cluster at 40°C and 80% relative humidity: E interaction =E total -E water -E cluster =-5317.417 kcal / mol.

[0101] Implementation Example 15:

[0102] Step 1: Calculate the water molecule density under standard atmospheric pressure, 40°C, and 90% relative humidity to be approximately 4.603×10 -5 g / cm 3 .

[0103] Step 2: Import the cif file of the AN crystal into the Materials Studio 2019 simulation software, perform a complete structural optimization on the AN initial unit cell to make the system architecture more reasonable, and set the calculation accuracy of the structural optimization to Ultra-fine (Energy: 2×10 -5 kcal / mol,Force:0.001kcal / mol / ), Displacement is set to Then construct the radius The constructed AN nanoclusters are placed on the side length The water molecule density calculated in the previous step is 4.603×10 -5 g / cm 3 Multiply by 200 to get 0.00921 g / cm 3 (≥0.0001g / cm 3 In line with the software modeling requirements), water molecules of this density are filled into the gaps between the AN clusters and the cubic lattice.

[0104] Step 3: The constructed AN moisture absorption model was simulated by molecular dynamics simulation of NVT using the Forcite module of Materials studio simulation software. The molecular dynamics time was set to 100ps. Finally, the last frame model after the molecular dynamics calculation was taken out, and the Forcite module was used to perform structural optimization operations without optimizing the unit cell to eliminate the unstable factors such as stress in the structure, and obtain a stable model after moisture absorption. The calculation accuracy of the structural optimization was set to Ultra-fine (Energy: 2×10 -5kcal / mol,Force:0.001kcal / mol / ), Displacement is set to

[0105] Step 4: Use the atom selection function to split the above stable model of AN after moisture absorption, and separate the model of single water molecules after moisture absorption, the model of single energetic molecular clusters, and the moisture absorption model of the complete system. Use the Forcite module to calculate the system energy of these three separation models, which are: E water =-3156.338 kcal / mol,E cluster =-73138.980 kcal / mol,E total =-81965.632 kcal / mol. Finally, the energy of the complete system after moisture absorption minus the energy of the individual energetic molecular cluster and then minus the energy of the individual water molecule is used to obtain the water molecule interaction energy of the AN spherical cluster at 40°C and 90% relative humidity: E interaction =E total -E water -E cluster =-5670.314 kcal / mol.

[0106] Data Analysis:

[0107] It can be seen from Examples 1 to 10 that when the relative humidity of the environment increases from 10% to 100% at 40° C., the hygroscopicity of ADN gradually increases (Table 1), and the simulation results are consistent with the actual results.

[0108] Table 1 Interaction energy between ADN and water molecules in Examples 1 to 10 (40°C)

[0109]

[0110] It can be seen from Examples 4, 11, 12, and 13 that when the ambient temperature increases from 0° C. to 60° C. at a relative humidity of 40%, the hygroscopicity of ADN increases gradually (Table 2), and the simulation results are consistent with the actual results.

[0111] Table 2 Interaction energy between ADN and water molecules in Examples 4, 11, 12, and 13 (40% RH)

[0112]

[0113] It can be seen from Examples 8, 9, 14, and 15 that when ADN and AN are both at 40°C, as the ambient temperature increases, the hygroscopicity gradually increases, and ADN is more hygroscopic than AN under the same environment (Table 3). The simulation results are consistent with the actual results.

[0114] Table 3 Interaction energy between ADN and AN and water molecules in Examples 8, 9, 14, and 15 (40°C)

[0115]

[0116]

[0117] The method of the invention will play an important role in the evaluation of the hygroscopicity of energetic materials and the prediction of the modification effect of hygroscopic energetic materials, and is also suitable for the evaluation of the hygroscopicity of non-energetic materials.

Claims

1. A method for evaluating the hygroscopicity of energetic materials under different temperature and humidity conditions, characterized in that: The specific steps include: The first step is to import the standard cif file of the initial unit cell of energetic molecules into the Materials Studio molecular simulation software, construct energetic molecular clusters of a certain size, and place the constructed energetic molecular clusters in a larger cubic grid. Water molecules with a known density under specific temperature and relative humidity conditions multiplied by n are filled into the space between the energetic molecular clusters and the cubic grid to construct the initial model. The second step is to perform NVT molecular dynamics calculation on the constructed initial model, take out the last frame model after the molecular dynamics calculation, and use the Forcite module to perform structural optimization of the non-optimized unit cell to eliminate the structural instability factors in the structure, and obtain the stable model M after moisture absorption; The third step is to decompose the stable model M after moisture absorption, and extract the model M1 of single water molecules after moisture absorption and the model M2 of single energetic molecular clusters. Use the Forcite module to calculate the system energy of these three models, that is, the energy E of M1 water 、Energy of M2 cluster 、Energy of M total Finally, the interaction energy E between the energetic molecular cluster and water molecules under specific temperature and relative humidity conditions is obtained. interaction The hygroscopicity of the energetic molecular clusters was evaluated by the interaction energy between the energetic molecular clusters and water molecules under different temperature and relative humidity conditions.

2. The evaluation method according to claim 1, characterized in that: Energetic molecular clusters of a certain size are In a larger cubic grid, the side length of the grid is 3. The evaluation method according to claim 1, wherein: In the first step, the specific temperature and relative humidity conditions refer to a temperature of 0 to 100° C. and a relative humidity of 0% to 100%.

4. The evaluation method according to claim 1, wherein: In the first step, the water molecule with known density under specific temperature and relative humidity conditions is multiplied by n times to make the density of the water molecule ≥ 0.0001 g / cm 3 Meet the modeling requirements of Materials studio molecular simulation software.

5. The evaluation method according to claim 1, wherein: In the second step, when performing NVT molecular dynamics calculations, the dynamic parameters are set, including: the time is set to 20ps~1000ps, the temperature control method adopts the Nose method, the calculation accuracy of the structure optimization is greater than or equal to the default Middle accuracy of the Forcite module, and the displacement factor needs to be considered.

6. The evaluation method according to claim 1, wherein: In the third step, E is determined according to the following formula: interaction : AND interaction =And total -AND water -AND cluster 。 7. The evaluation method according to claim 1, characterized in that: In the third step, the energy calculation accuracy of each model is greater than or equal to the default Middle accuracy of the Forcite module of Materials studio software.

8. The evaluation method according to claim 1, wherein: In the third step, the interaction energy E of energetic molecular clusters with water molecules under different temperature and relative humidity conditions is measured. interaction , the hygroscopicity of the energetic molecular clusters was evaluated, E interaction The larger the absolute value of is, the stronger the hygroscopicity of the energetic molecular clusters is.

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