Microcosmic parameter-based environment-friendly insulating gas high-temperature cracking trajectory analysis method

Abstract

The invention discloses an environment-friendly insulating gas high-temperature cracking trajectory analysis method based on microscopic parameters, which comprises the following steps: step 1, optimizing environment-friendly insulating gas molecules to obtain a stable single-molecule configuration; 2, calculating microcosmic parameters of environment-friendly insulating gas molecules, wherein the microcosmic parameters comprise a Fukui function f (0) of a free radical reaction, a Fukui function f (-) of a nucleophilic reaction, a Fukui function f (+) of an electrophilic reaction and a Mayer bond level; step 3, constructing a structure model of the environment-friendly insulating gas system in high-temperature cracking reaction; 4, simulating high-temperature cracking of the environment-friendly insulating gas in a ReaxFF force field based on a first principle; and 5, generating a high-temperature cracking track file of the environment-friendly insulating gas by using an lmp2arc toolkit based on a Rocky system, and observing a reaction track. Based on the microscopic atomic angle, the high-temperature cracking reaction track which cannot be completely observed under the macroscopic experiment can be obtained, the reaction path of the typical environment-friendly insulating gas is consistent with that observed by the experiment, and reliability is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of quantum chemical calculation and molecular dynamics simulation, and more specifically to an environmentally friendly insulating gas high-temperature cracking trajectory analysis method based on microscopic parameters. Background Art

[0002] Sulfur hexafluoride gas SF 6 As an insulating and arc-extinguishing gas, it is widely used in the power industry, but SF 6 Gases have a high global warming potential (GWP) (approximately 2 23900 times), and SF 6 Decomposition products SO 2 、SOF 2 It is highly corrosive and extremely harmful to the environment. 6 Environmental issues of SF have prompted researchers to focus on the development of environmentally friendly insulating gases. Since 1992, the United Nations Framework Convention on Climate Change, the Kyoto Protocol, and the Paris Agreement have proposed limiting the use of SF 6 The use of gas, so far, environmentally friendly insulating gas has gradually begun to replace sulfur hexafluoride gas in power equipment.

[0003] However, most environmentally friendly insulating gases are colorless, and due to the limitations of observation instruments, it is difficult to observe the high-temperature cracking process of environmentally friendly insulating gases in real time. In recent years, many researchers have tried to observe the high-temperature cracking process of environmentally friendly insulating gases from a microscopic perspective based on first principles, but due to the problems of diverse reaction pathways, rapid cracking process, and difficulty in observing free radical intermediates that are prone to reaction, it is difficult to observe the high-temperature cracking trajectory of environmentally friendly insulating gases. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a method for analyzing the high-temperature cracking trajectory of environmentally friendly insulating gas based on microscopic parameters, and uses the lmp2arc toolkit to draw the high-temperature cracking trajectory of the environmentally friendly insulating gas.

[0005] To achieve the above purpose, a method for analyzing the high temperature cracking trajectory of an environmentally friendly insulating gas based on microscopic parameters comprises the following steps:

[0006] Step 1: Build a molecular model of the environmentally friendly insulating gas in the molecular simulation software Materials Studio, and perform geometry optimization based on the first principles using PBE / DNP functional and basis set levels to obtain a stable structure with the lowest molecular energy;

[0007] Step 2: In the DMol3 module of Materials studio software, use the PBE / DNP functional and basis set to perform further energy calculations on the environmentally friendly insulating gas molecules optimized in step 1, thereby obtaining the microscopic parameters of the environmentally friendly insulating gas molecules, and predicting the cracking reaction sites of the environmentally friendly insulating gas based on the microscopic parameters;

[0008] Step 3, constructing a reaction system model of the environmentally friendly insulating gas, and performing geometric optimization to obtain a minimum energy system conformation, and adjusting the initial temperature and density of the environmentally friendly insulating gas reaction system model according to the actual temperature and density;

[0009] Step 4, using the ReaxFF force field to perform high-temperature cracking simulation on the adjusted environmentally friendly insulating gas reaction system model, and obtain a dump file generated by high-temperature cracking of the environmentally friendly insulating gas;

[0010] Step 5: In the Rocky system, the dump file generated by the high-temperature cracking simulation is used as the input file of the lmp2arc toolkit to generate a high-temperature cracking trajectory file of the environmentally friendly insulating gas. The trajectory file is opened using the Animation toolkit of the Materials Studio software to observe the reaction trajectory animation.

[0011] Preferably, in step 2, the microscopic parameters include the Fukui function f(0) of free radical reaction, the Fukui function f(-) of nucleophilic reaction, the Fukui function f(+) of electrophilic reaction, and the Mayer bond order.

[0012] Preferably, in step 3, the reaction system model is established using the Amorphous Cell module of the Materials Studio software, and the initial density is set to 0.8 g / cm3 and the initial temperature is set to 298 K; the density and temperature of the environmentally friendly insulating gas reaction system model are adjusted by performing 50 ps relaxation in the NVT ensemble and the NPT ensemble respectively.

[0013] Preferably, in step 4, the adjusted environmentally friendly insulating gas reaction system model is simulated for high temperature cracking using the ReaxFF force field, and the system energy of the ReaxFF force field is calculated as follows:

[0014] E system =E bond +E over +E under +E val +E pen +E tors +E lp +E coa +E vdWaals +E Coulomb +ESpecific

[0015] E bond =-D e α BOij ·exp[p bond1 (1-(α BOij ) pbond2 )]

[0016] E val =f 1 (α BOij )·f 1 (α BOik )·f 3 (Δ j )·{p val1 -p val1 ×exp[-p val2 ×(θ 0 -θ ijk ) 2 ]}

[0017] E pen =p pen1 ·f 4 (Δ j )·exp[-p pen2 (α BOij -2) 2 ]·exp[-p pen2 (α BOjk -2) 2 ]

[0018] In the formula, E system is the total energy of the system, E bond is the bond energy, E over and E under represents the over- and under-coordination energy correction in the energy contribution, E val represents the energy of covalent bond angle bending, E pen represents the penalty energy for an atom to share two double bonds and destabilize the system, E tors is the torsional energy, E conj represents the energy conjugation effect, E lp represents the energy of the lone pair of electrons, E coa represents the three-point conjugation energy, E Specific Indicates the special energy contribution to a specific molecular system, such as four-point conjugation, hydrogen bonding and C 2 The energy portion affected by the correction, E vdwaals and E coulomb are the non-bonded van der Waals interaction and the non-bonded Coulomb interaction, respectively. BOij , α BOik is the corrected bond order, D eis the key parameter, Δ j is the coordination number, θ 0 is the equilibrium bond angle, θ ijk is the interatomic bond angle, P bond1 is a parameter used to describe the initial strength and stiffness of the bond, P val1 is the parameter associated with the initial value of the key level, P pen1 P is a parameter used to indicate the slope or curvature of the interatomic interaction force at a specific bond length. bond2 , P val2 , P pen2 These are parameters used to adjust the shape of the key curve.

[0019] Further preferably, the high temperature cracking simulation is divided into 6 temperature gradients for control experiments (2000K, 2200K, 2400K, 2600K, 2800K, 3000K), and a 1000ps molecular dynamics simulation is performed based on the NVT ensemble.

[0020] Preferably, in step 4, the dump file is obtained by modifying the dump command of the molecular simulation software lammps before the high temperature cracking simulation. The modified dump command format is: dump 1all custom 1000name.dump idtypexs ys zs ix iy iz dump_modify 1sort-1

[0021] Preferably, in step 5, the specific process of generating the high-temperature cracking trajectory file of the environmentally friendly insulating gas includes: using Materials Studio to export the environmentally friendly insulating gas reaction system model without adjusting the density and temperature as a car file; then placing the dump file, the car file, and the lmp2arc.exe file that comes with the lammps software in the same folder and running the lmp2arc toolkit to obtain the trajectory file.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention provides a method for analyzing the high-temperature cracking trajectory of an environmentally friendly insulating gas based on microscopic parameters. The microscopic parameters of the environmentally friendly insulating gas are studied based on the first principles, thereby predicting and analyzing the cracking reaction sites of the environmentally friendly insulating gas, and providing a basis for verifying the rationality of the high-temperature cracking trajectory of the environmentally friendly insulating gas; based on the lmp2arc toolkit provided by the molecular simulation software lammps, the dump file output by the high-temperature cracking simulation is converted into a trajectory file, and the trajectory animation is viewed using the Animation module of Materials Studio, so as to observe the high-temperature cracking process of the environmentally friendly insulating gas from the atomic scale. The present invention can provide theoretical guidance for predicting the cracking reaction sites of environmentally friendly insulating gases and dynamically observing the high-temperature cracking trajectory of environmentally friendly insulating gases; at the same time, it also paves the way for subsequent research on calculating the high-temperature cracking reaction path. At the same time, it can also provide a reference for trajectory analysis of other types of molecular simulations. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flow chart for generating an animation of the trajectory of the high-temperature cracking reaction of an environmentally friendly insulating gas.

[0025] Figure 2 Environmentally friendly insulating gas C 4 F 7 N is the optimized molecular configuration, with each atom numbered separately.

[0026] Figure 3 Environmentally friendly insulating gas C 4 F 7 Fukui function of N, (a) is the Fukui function f(0) of free radical reaction, (b) is the Fukui function f(-) of nucleophilic reaction, and (c) is the Fukui function f(+) of electrophilic reaction.

[0027] Figure 4 It is an environmentally friendly insulating gas C 4 F 7 Animation of the high-temperature decomposition trajectory of N. (a) shows the decomposition state at 1ps, (b) shows the decomposition state at 10ps, and (c) shows the decomposition state at 100ps. DETAILED DESCRIPTION

[0028] The following is a clear and complete description of the technical solution in the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The present invention proposes a method for analyzing high-temperature cracking trajectories of an environmentally friendly insulating gas based on microscopic parameters, comprising the following steps:

[0030] Step 1: Build a molecular model of the environmentally friendly insulating gas in the molecular simulation software Materials Studio, and perform geometry optimization based on the first principles using PBE / DNP functional and basis set levels to obtain a stable structure with the lowest molecular energy;

[0031] Step 2: In the DMol3 module of Materials studio software, use the PBE / DNP functional and basis set to perform further energy calculations on the environmentally friendly insulating gas molecules optimized in step 1, thereby obtaining the microscopic parameters of the environmentally friendly insulating gas molecules, and predicting the cracking reaction sites of the environmentally friendly insulating gas based on the microscopic parameters;

[0032] Step 3, constructing a reaction system model of the environmentally friendly insulating gas, and performing geometric optimization to obtain a minimum energy system conformation, and adjusting the initial temperature and density of the environmentally friendly insulating gas reaction system model according to the actual temperature and density;

[0033] Step 4, using the ReaxFF force field to perform high-temperature cracking simulation on the adjusted environmentally friendly insulating gas reaction system model, and obtain a dump file generated by high-temperature cracking of the environmentally friendly insulating gas;

[0034] Step 5: In the Rocky system, the dump file generated by the high-temperature cracking simulation is used as the input file of the lmp2arc toolkit to generate a high-temperature cracking trajectory file of the environmentally friendly insulating gas. The trajectory file is opened using the Animation toolkit of the Materials Studio software to observe the reaction trajectory animation.

[0035] Example 1

[0036] A molecular model of an environmentally friendly insulating gas is constructed in the molecular simulation software Materials Studio. Based on first principles, geometry optimization is performed using the PBE / DNP functional and basis set levels to obtain a stable structure with the lowest molecular energy.

[0037] In specific implementation, the initial molecular model provided by the ChemSpider database can be used, or the environmentally friendly insulating gas C can be drawn in software such as GaussianView and AMS. 4 F 7 The molecular structure model of N was optimized using the PBE / DNP functional and basis set level of the DMol3 module in Materials Studio software to obtain the stable configuration with the minimum energy, such as Figure 2 shown.

[0038] Example 2

[0039] In the DMol3 module of Materials studio software, the PBE / DNP functional and basis set are used to perform further energy calculations on the environmentally friendly insulating gas molecules optimized in step 1, so as to obtain the microscopic parameters of the environmentally friendly insulating gas molecules and predict the cracking reaction sites of the environmentally friendly insulating gas based on the microscopic parameters.

[0040] In the specific implementation, in the Materials studio software, for the optimized C 4 F 7 Select GGA-PBE functional in the setup interface of DMol3 module for N molecule, select DNP-3.5 basis set in Electronic interface, use DllS to build subspace to accelerate convergence, check Electron density, Electrostatics, Fukui function, population analysis in Properties interface, and calculate C 4 F 7 The Fukui function of N molecules (such as Figure 3 As shown), Mayer bond order (as shown in Table 1), where the Fukui function reflects the reaction site during electrophilic attack and nucleophilic attack, and the Mayer bond order reflects the bond breaking order.

[0041] Table 1C 4 F 7 Mayer bond order of N molecule

[0042]

[0043] Example 3

[0044] Construct a reaction system model of environmentally friendly insulating gas, perform geometric optimization, obtain the minimum energy system conformation, and adjust the initial temperature and density of the reaction system model of environmentally friendly insulating gas according to the actual temperature and density;

[0045] In the specific implementation, the Amorphous Cell module of Materials Studio software was used to set the initial density to 0.8 g / cm3 and the initial temperature to 298 K to establish C 4 F 7The box model of N gas was exported as car file and mdf file. Then, the car file and mdf file were converted into data file with the help of insight2lammps.pl tool provided by lammps software as the initial input file for lammps high temperature cracking simulation. Finally, based on NVT ensemble, 50ps relaxation was performed at 300K to relax the molecular structure to equilibrium state, and then 50ps relaxation was performed under NPT ensemble to adjust C 4 F 7 The density of the N gas reaction system model is obtained by adjusting the C 4 F 7 N gas reaction system model. The NVT ensemble uses the Nose-Hoover heat bath method to control temperature, and the temperature damping constant is 5 fs. The NPT ensemble uses the Berendsen method to control pressure, and the pressure damping constant is 5 fs.

[0046] Example 4

[0047] The ReaxFF force field is used to simulate the high-temperature cracking of the adjusted environmentally friendly insulating gas reaction system model to obtain the dump file generated by the high-temperature cracking of the environmentally friendly insulating gas.

[0048] In the specific implementation, for the adjusted C 4 F 7 N gas reaction system model, using ReaxFF-MD method to perform 1000ps NVT high temperature cracking reaction at 2000K, 2200K, 2400K, 2600K, 2800K, and 3000K. The NVT temperature control method adopts Nose-Hoover heat bath method with a temperature damping constant of 5fs. After the simulation, a dump file is output.

[0049] More specifically, before the high temperature cracking simulation, the default dump command format of the lammps software is modified. The modified dump command format is:

[0050] dump 1all custom 1000name.dump idtype xs ys zs ix iy iz

[0051] dump_modify 1sort-1

[0052] Example 5

[0053] In the Rocky system, the dump file generated by the high-temperature cracking simulation is used as the input file of the lmp2arc toolkit to generate the high-temperature cracking trajectory file of the environmentally friendly insulating gas. The trajectory file is opened using the Animation toolkit of the Materials Studio software to observe the reaction trajectory animation.

[0054] In the specific implementation, in the Rocky system, C 4 F 7 Put the car file exported by the N gas box model, the dump file output by the high temperature cracking simulation, and the lmp2arc.exe file that comes with lammps in the same folder, open it in the terminal, run the lmp2arc toolkit, and enter the following commands in sequence: lmp2arc.exe folder path -trueflags-move_mol-car Read the file name .car< <eof> Output file name .arc; Folder path for dump files ; EOF

[0055] get Output file name .arc file, open it with Materials Studio in Windows and use the Animation tool to observe the C 4 F 7 Animation of the high-temperature cracking trajectory of N gas, such as Figure 4 shown.

[0056] The above content is merely an illustration of the structure of the present invention. The technicians in this technical field may make various modifications or additions to the specific structure described. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.< / eof>

Claims

1. A method for analyzing high-temperature cracking trajectory of environmentally friendly insulating gas based on microscopic parameters, characterized in that: The following steps are involved: Step 1: Build a molecular model of the environmentally friendly insulating gas in the molecular simulation software Materials Studio, and perform geometry optimization based on the first principles using PBE / DNP functional and basis set levels to obtain a stable structure with the lowest molecular energy; Step 2: In the DMol3 module of Materials studio software, use the PBE / DNP functional and basis set to perform further energy calculations on the environmentally friendly insulating gas molecules optimized in step 1, thereby obtaining the microscopic parameters of the environmentally friendly insulating gas molecules, and predicting the cracking reaction sites of the environmentally friendly insulating gas based on the microscopic parameters; Step 3, constructing a reaction system model of the environmentally friendly insulating gas, and performing geometric optimization to obtain a minimum energy system conformation, and adjusting the initial temperature and density of the environmentally friendly insulating gas reaction system model according to the actual temperature and density; Step 4, using the ReaxFF force field to perform high-temperature cracking simulation on the adjusted environmentally friendly insulating gas reaction system model, and obtain a dump file generated by high-temperature cracking of the environmentally friendly insulating gas; Step 5: In the Rocky system, the dump file generated by the high-temperature cracking simulation is used as the input file of the lmp2arc toolkit to generate a high-temperature cracking trajectory file of the environmentally friendly insulating gas. The trajectory file is opened using the Animation toolkit of the Materials Studio software to observe the reaction trajectory animation.

2. The method according to claim 1, characterized in that: In the step 2, the microscopic parameters include the Fukui function f(0) of the free radical reaction, the Fukui function f(-) of the nucleophilic reaction, the Fukui function f(+) of the electrophilic reaction, and the Mayer bond order.

3. The method according to claim 1, characterized in that: In step 3, the reaction system model is established using the Amorphous Cell module of the Materials Studio software, with the initial density set to 0.8 g / cm3 and the initial temperature set to 298 K; the density and temperature of the environmentally friendly insulating gas reaction system model are adjusted by performing 50 ps relaxation in the NVT ensemble and the NPT ensemble respectively.

4. The method according to claim 1, characterized in that: In step 4, the ReaxFF force field is used to perform high-temperature cracking simulation on the adjusted environmentally friendly insulating gas reaction system model. The system energy of the ReaxFF force field is calculated as follows: AND system =And bond +E over +E under +E val +E pen +E tors +E lp +E coa +E vdWaals +E Coulomb +E Specific E val =f1(a BOij )·f1(a BOik )·f3(D j )·{p val1 -p val1 ×exp[-p val2 ×(θ0-θ ijk ) 2 ]} From pen =p pen1 ·f4(Δ j )·exp[-p pen2 (α BOij -2) 2 ]·exp[-p pen2 (α BOjk -2) 2 ] In the formula, E system is the total energy of the system, E bond is the bond energy, E over and E under represents the over- and under-coordination energy correction in the energy contribution, E val represents the energy of covalent bond angle bending, E pen represents the penalty energy for an atom sharing two double bonds to destabilize the system, E tors is the torsional energy, E conj represents the energy conjugation effect, E lp represents the energy of the lone pair of electrons, E coa represents the three-point conjugation energy, E Specific It represents the special energy contribution for a specific molecular system, such as the energy part affected by four-point conjugation, hydrogen bonding and C2 correction, E vdwaals and E coulomb are the non-bonded van der Waals interaction and the non-bonded Coulomb interaction, respectively. BOij , α BOik is the corrected bond order, D e is the key parameter, Δ j is the coordination number, θ0 is the equilibrium bond angle, θ ijk is the interatomic bond angle, P bond1 is a parameter used to describe the initial strength and stiffness of the bond, P val1 is the parameter associated with the initial value of the key level, P pen1 P is a parameter used to indicate the slope or curvature of the interatomic interaction force at a specific bond length. bond2 , P val2 , P pen2 These are parameters used to adjust the shape of the key curve.

5. The method according to claim 1, characterized in that: In step 4, the high temperature cracking simulation is divided into 6 temperature gradients for control experiments (2000K, 2200K, 2400K, 2600K, 2800K, 3000K), and a 1000ps molecular dynamics simulation is performed based on the NVT ensemble.

6. The method according to claim 1, characterized in that: In step 4, the dump file is obtained by modifying the dump command in the molecular simulation software lammps before the high temperature cracking simulation.

7. The method according to claim 1, characterized in that: In step 5, the specific process of generating the high-temperature cracking trajectory file of the environmentally friendly insulating gas includes: using Materials Studio to export the environmentally friendly insulating gas reaction system model without adjusting the density and temperature as a car file; then placing the dump file, car file, and lmp2arc.exe file in the same folder and running the lmp2arc toolkit to obtain the trajectory file.

Images