Method and apparatus for non-equilibrium molecular dynamics simulation under planar couette flow field of confined linear / non-linear polyethylene melt within interface

Abstract

The present invention presents a method for a non-equilibrium molecular dynamics simulation under a planar Couette flow field of a confined linear / nonlinear polyethylene melt within an interface. A simulation apparatus of the present invention comprises: an input module for receiving an input of information required in a molecular dynamics simulation of a polymer; a calculation module for calculating, on the basis of the information that was input, the properties of the polymer by performing the molecular dynamics simulation while applying a reversible reference system propagation algorithm (r-RESPA) to a p-SLLOD equation; a storage module for storing, by designated time unit, the calculated properties; and an output module for outputting information about the stored properties.

Description

Method and device for nonequilibrium molecular dynamics simulation under planar COUETTE flow field of linear / nonlinear polyethylene melt confined within interface

[0001] The present invention relates to a molecular dynamics (MD) simulation method and device capable of identifying properties or characteristics of polymers that are difficult to confirm in an actual experimental stage, as well as the movement of each polymer at the micro-molecular level.

[0002] Polymers are widely used across industries. To improve the various properties of these polymers and manufacture specific processed products, an understanding of their properties, characteristics, and features is essential from the processing stage onward.

[0003] However, without simulation, theory and experimentation are time-consuming and difficult to quickly and accurately determine the properties, characteristics, and characteristics of polymers. For example, many theories have been proposed to improve the various physical properties of polymers, but each of these theories requires various assumptions and hypotheses, and verifying and comparing them is difficult. Furthermore, even when conducting actual experiments, there are constraints. For example, experiments cannot be conducted under input conditions such as extremely low temperatures, high temperatures, or extreme temperatures. Furthermore, experiments cannot observe the movement of molecules and atoms.

[0004] Especially during the forming and processing stages of polymers, polymers often exist in an interfacial state. Understanding the shape and behavior of polymers in this interfacial state is crucial for understanding their physical properties and specific phenomena. However, confirming the state of polymers in this interfacial state through theory and experimentation is difficult.

[0005] The present invention has been devised to solve the above problems, and provides a simulation method and device that can directly implement the properties or characteristics of polymers, which are difficult to obtain through theory or experiment, and the movement of each polymer at the micro-molecular level.

[0006] The present invention enables calculation of various polymer properties such as viscosity, pressure, shear, and normal stress through analysis of molecular level information obtained through simulation.

[0007] The present invention provides simulation results that enable prediction and improvement of polymer rheological properties.

[0008] The technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0009] In order to achieve the above object, a simulation device according to an embodiment of the present invention comprises: an input module for receiving information required for molecular dynamics simulation of a polymer; a calculation module for performing molecular dynamics simulation by applying r-RESPA (reversible Reference System Propagation Algorithm) to the p-SLLOD equation based on the input information to calculate properties of the polymer; a storage module for storing the calculated properties in a specified time unit; and an output module for outputting the stored property information.

[0010] The above p-SLLOD equation is as follows, and the equation above is to keep the simulation temperature constant. -Hoover thermostat is also applied.

[0011]

[0012] Here, the above refers to the actual nonlinear velocity distribution of polymers calculated by a polynomial fitting algorithm in an interfacial system.

[0013] The above calculation module includes a first calculation unit that calculates position and velocity information of a polymer chain; and a second calculation unit that calculates structural and dynamic properties of the polymer using the position and velocity information.

[0014] The above calculation module uses a Lennard-Jones potential function with attractive and repulsive terms depending on the distance between atoms, and a Linked cell and Neighbor list method that considers only neighbor atoms depending on the distance between atoms.

[0015] The above output module can observe the movement of the polymer chain through a visualization program.

[0016] It further includes a re-run module that performs whether to re-run the above simulation, and the re-run module stores system information about the last calculated time so that the simulation can be restarted from the point where the simulation was stopped if the simulation was stopped.

[0017] Information required for the above simulation may include initial system environment information including time, temperature, density, shear flow intensity, and simulation time interval; and initial system structure information including the number of molecular chains (nmol), the total number of particles (npartcl), the number and length of branches existing in each chain, the number of particles forming the interface (npartcl_uw, bw), the size of the simulation system box (boxleng), and initial position information for each particle.

[0018] A simulation method according to another embodiment of the present invention is performed including an acquisition step of acquiring information necessary for molecular dynamics simulation of a polymer; a calculation step of performing molecular dynamics simulation based on the acquired information to calculate properties of the polymer; and a storage step of storing the calculated properties in a specified time unit.

[0019] The above calculation step calculates (integrates) each MD step using r-RESPA (reversible Reference System Propagation Algorithm) for the p-SLLOD equation for the current simulation.

[0020] The above calculation step calculates the properties using the following equation, and when calculating the properties, the simulation temperature is kept constant. -Hoover thermostat applies.

[0021]

[0022] Here, the above refers to the actual nonlinear velocity distribution of polymers calculated by a polynomial fitting algorithm in an interfacial system.

[0023] The above calculation step may include a first calculation step of calculating position and velocity information of a polymer chain; and a second calculation step of calculating structural and dynamic properties of the polymer using the position and velocity information.

[0024] The above calculation step can use the Lennard-Jones potential function having attractive and repulsive terms depending on the distance between atoms.

[0025] Prior to the above acquisition step, an input step may further be included for receiving information on the initial system environment and initial system structure required for performing the simulation.

[0026] The above initial system environment information includes time, temperature, density, shear flow intensity, and simulation time interval, and the above initial system structure information includes the number of molecular chains (nmol), the total number of particles (npartcl), the number and length of branches existing in each chain, the number of particles forming the interface (npartcl_uw, bw), the size of the simulation system box (boxleng), and initial position information for each particle.

[0027] According to the present invention, factors affecting polymer properties can be accurately identified and systematically simulated through simulation.

[0028] According to the present invention, polymer rheological properties can be predicted and improved in an actual process based on simulation results.

[0029] According to the present invention, the shape and movement of a polymer in an interface state that is difficult in actual experiments can be realized, and molecular level information can be used to calculate various polymer properties such as viscosity, pressure, shear, and normal stress through analysis.

[0030] According to the present invention, it is possible to study not only the steady state of a polymer but also the transient behavior of the polymer.

[0031] Figures 1a and 1b are diagrams illustrating the interface system environment of a polymer.

[0032] Figure 2 is a diagram showing the die swell phenomenon of a polymer in an interface environment.

[0033] Figure 3 is a diagram showing linear and nonlinear polymer structures.

[0034] Figure 4 is a graph showing the change in glass transition temperature depending on the degree of branching of a nonlinear polymer.

[0035] FIGS. 5 to 7 are drawings for explaining the simulation conditions of the present invention for calculating the velocity distribution in a planar couette flow field, 2D PBC, and transient state study.

[0036] Figure 8 is a configuration diagram of a simulation device according to an embodiment of the present invention.

[0037] Figure 9 is a flowchart explaining a simulation method according to an embodiment of the present invention.

[0038] Figures 10 and 11 are exemplary drawings illustrating non-equilibrium molecular dynamics according to an embodiment of the present invention.

[0039] The present invention is susceptible to various modifications and embodiments, and specific embodiments are illustrated and described in detail in the drawings. However, this is not intended to limit the present invention to specific embodiments, and it should be understood that all modifications, equivalents, and alternatives included within the spirit and technical scope of the present invention are included. In describing the present invention, if a detailed description of a related known technology is judged to obscure the gist of the present invention, the detailed description will be omitted.

[0040] Terms such as first, second, etc. may be used to describe various components, but these components should not be limited by these terms. These terms are used solely to distinguish one component from another.

[0041] The terminology used herein is merely used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0042] Expressions such as “part” or “section” used in the present invention to indicate a part mean that the corresponding component may indicate a device that can include a specific function, software that can include a specific function, or a combination of a device and software that can include a specific function, but are not necessarily limited to the expressed function. This is provided only to help a more general understanding of the present invention, and those skilled in the art to which the present invention pertains can make various modifications and variations based on this description.

[0043] Therefore, the idea of ​​the present invention should not be limited to the described embodiments, and all things that are equivalent or equivalent to the claims described below as well as the claims are considered to fall within the scope of the idea of ​​the present invention.

[0044]

[0045]

[0046] Hereinafter, the present invention will be described in more detail based on embodiments illustrated in the drawings.

[0047]

[0048] To understand the present invention, we will look at various types of simulations.

[0049] Simulations can be categorized based on their time and length scales. For example, quantum simulations are used in catalysis, where electrical properties related to electron movement are crucial. Molecular dynamics (MD) simulations are used when the movement of actual atoms or molecules, such as protein-protein interactions, is crucial. Continuum simulations are used when the goal is to understand the overall fluid flow and properties beyond the molecular level.

[0050] Among these, molecular dynamics simulations are used to observe physical phenomena with time scales typically in the hundreds of nanoseconds (ns) and length scales up to hundreds of nanometers (nm). This allows for the direct simulation of molecular motion. Simulation programs used in molecular dynamics include LAMMPS, CHARMM, GROMACS, AMBER, and NAMD.

[0051] In the interfacial system of the present invention, a slip phenomenon occurs due to the presence of a wall. The degree of this slip is affected by various characteristics of the interfacial system, such as the type of wall atoms, the length of the polymer chain, the strength of the flow field, temperature, density, etc., and the degree of slip can be quantitatively calculated in the present invention. In addition, as slip occurs, the velocity distribution within the interfacial system naturally becomes nonlinear, and this can be accurately obtained through the fitting algorithm of the present invention.

[0052] Because polymers exhibit unique phenomena depending on the presence or absence of interfaces and their microstructure, research on interfacial systems is essential. As mentioned earlier, the shape and behavior of polymers at interfaces are crucial for understanding their physical properties and specific phenomena.

[0053] Therefore, the present invention proposes a simulation method for polymers, and such simulation can be explained through four characteristic items: polymer interface state, linear / nonlinear structure, planar Couette flow, and non-equilibrium molecular dynamics.

[0054] And the embodiment of the present invention, which will be examined below, discloses a simulation method targeting polyethylene polymer. However, it will be obvious that the present invention can simulate other polymer materials by applying an appropriate force-field (potential) molecular model. In addition, the simulation of the present invention can conduct precise research on not only the steady-state but also the transient behavior of the polymer system that changes over time at the beginning of the simulation by directly calculating and applying the average velocity according to the position within the system at each moment under an external flow field. In addition, the MPI (Message Passing Interface) standard for efficient parallel computing was also applied.

[0055]

[0056] Polymer interface state

[0057] Figures 1a and 1b are diagrams illustrating the interface system environment of a polymer.

[0058] Observing polymer motion according to the strength of the flow field in an interfacial environment can be a crucial factor in overall polymer processing. In Figure 1, the interfacial region refers to the area close to the interface (wall). The area between the interfacial regions can be considered the bulk region. The bulk region can be located in the central portion of the pipe.

[0059] However, in principle, polymers in the interfacial region close to the wall and polymers in the bulk region slightly away from the wall may experience different influences from the wall within the same system. However, this difference is subtle. Ultimately, since the entire interfacial system is influenced by the wall, the entire system can be considered an interfacial region.

[0060]

[0061] Figure 2 is a diagram showing the die swell phenomenon of a polymer in an interface environment.

[0062] As shown in Fig. 2, die swell, which occurs when molding a polymer using a die, refers to a phenomenon in which the volume of the polymer expands after injection.

[0063] Polymers possess an elasticity that tends to return to their original state. Simply put, at the molecular level, polymer chains are primarily spherical (the form where entropy is maximized) before injection (when the flow field is weak). However, upon entering the narrow mold (where the flow field is strong), they become relatively more stretched in the direction of the flow field, subjecting them to greater stress.

[0064] After passing through the tube, the flow field intensity decreases, the stress is relieved, and the material returns to its original spherical shape, increasing in volume.

[0065] At this time, various factors such as the viscosity and elastic recovery of the polymer itself, die length, vertical stress acting on the die wall, and temperature affect die swell, so these conditions must be appropriately controlled during polymer molding.

[0066]

[0067] Linear / nonlinear structure

[0068] Figure 3 is a diagram showing linear and nonlinear polymer structures.

[0069] As shown in Figure 3, polymers can be classified into linear polymers (a) and branched nonlinear polymers (b). It can be seen that linear polymers (a) and nonlinear polymers (b) have different dynamic properties and mechanisms.

[0070] Furthermore, nonlinear polymers (b) can also have different structures depending on the location and frequency of branching, which can lead to different physical properties. Ultimately, even within the same nonlinear polymer, by modifying the branches differently, a polymer with specific desired properties can be created.

[0071]

[0072] Figure 4 is a graph showing the change in the glass transition temperature (Tg) depending on the degree of branching of a nonlinear polymer. As shown in Figure 5, it can be confirmed that the glass transition temperature (Tg) gradually decreases as the degree of branching (DB) of the polymer increases.

[0073]

[0074] Planar Couette Flow

[0075] In the present invention, various flow fields can be applied to the polymer processing process. Among them, planar Couette flow is the most ideal and simple flow. When planar Couette flow is applied, the polymer below forms a linear velocity distribution along the y-axis due to the movement of the interface at the outer edge.

[0076] The present invention applies such a planar couette flow, so that polymers move along the movement of the wall as shown in Fig. 3. In addition, accurate velocity distribution calculation, 2D PBC, and simulation of the transient state are possible in the planar couette flow field.

[0077]

[0078] FIGS. 5 to 7 are drawings for explaining the simulation conditions of the present invention for calculating the velocity distribution in a planar couette flow field, 2D PBC, and transient state study.

[0079] Referring to Figure 6, which explains the calculation of the velocity distribution, when the upper particle forming the upper interface moves at a fixed velocity, momentum is transferred to the polymer at the interface, and the polymers below have their own velocities depending on their y-axis positions. At this time, other molecular dynamics programs assume that the result will be theoretically (ideally) linear and use that value as is, but the present invention calculates and applies the actual (real) velocity distribution using a 5th-order polynomial fitting.

[0080] Referring to Figure 7, which explains the 2D PBC (Periodic boundary condition), the simulation of the present invention performs the simulation by applying PBC only in the 2D direction of the x / z axes, without applying PBC in the y-axis, which is the direction in which the upper / lower walls exist.

[0081] Referring to Figure 8, which illustrates the transient state study, the initial state of the simulation is called the transient state. At this point, if a specific value is determined, the value may be unstable and not constant. However, if sufficient simulation time elapses, the steady state is reached, and the value becomes constant.

[0082] When a polymer is subjected to a constant external flow field, its stress value typically increases initially and then decreases, reaching a stable value. Therefore, when calculating the structural and dynamic properties of polymers through simulation, the average value is typically calculated from numerous samples of steady-state data obtained after the simulation has been sufficiently completed.

[0083] However, to understand the phenomenon of stress spikes early on, information about the transient state, the initial stage of the simulation, is required. In other words, to understand how stress occurs, an accurate description is needed not of the steady state, but of the transient state, which statistically represents an absolute lack of samples. The present invention enables the study of this transient state through simulation.

[0084]

[0085] Nonequilibrium molecular dynamics

[0086] Since an external flow field must be applied in a non-equilibrium state and the temperature must also be kept constant, it is necessary to apply an algorithm accordingly to the simulation of the present invention.

[0087] The actual speed distribution proposed by the present invention The p-SLLOD equation with added items can be derived through Newton's equation of motion F = ma.

[0088] If we apply the above equation F = ma to each of the simulation components, = It can be expressed in the form of (each atom i The force, mass, and acceleration corresponding to each , , (expressed as ).

[0089] At this time, the initial time Given the position r and velocity v of each particle, the force acting on each particle according to the potential model of the simulation can be calculated. For example, if there are three atoms in the simulation box, as in Fig. 10, (force acting on atom1) is (the force that atom2 gives to atom1) + (the force that atom3 gives to atom1) is expressed as

[0090] Through this, a specific time as shown in Fig. 11 The position and velocity information of particles can be obtained, and all properties required for the simulation can be calculated using this information. Here, the simulation time used for property calculation , that is, the more data points there are, the greater the statistical reliability.

[0091]

[0092] Meanwhile, in statistical mechanics, Newton's equations of motion, = is expressed as follows using the particle's position r and momentum p ( , ).

[0093] And the above formula , When a thermostat is applied, it becomes mathematical equation 1. The thermostat is a device that maintains a constant temperature, and this is possible by artificially controlling the velocity of particles. For example, when the temperature of the simulation system is momentarily high, the velocity of the particles is slowed down to reduce the temperature, and conversely, when the temperature of the system is low, the velocity of the particles is increased to raise the temperature, thereby maintaining a constant temperature in the simulation.

[0094]

[0095] Finally, using mathematical equation 1, mathematical equation 2 for simulating the present invention can be obtained.

[0096] Mathematical expression 2 is the external flow field term in the non-equilibrium state in which the present invention has a flow field. In a situation where only the actual velocity distribution is applied, we use a polynomial fitting algorithm to This is a p-SLLOD equation implemented more accurately by adding items. In other words, this embodiment calculates the p-SLLOD equation using r-RESPA (reversible reference system propagation algorithm) as in mathematical equation 2 below, and at this time, the temperature of the system is kept constant. -Hoover thermostat applies.

[0097]

[0098] In mathematical expression 2 is the shear velocity gradient tensor, which is the external flow field value given as input in the simulation, and the velocity distribution according to it should theoretically be linear. And the corresponding is the actual velocity distribution calculated in the simulation and is different from the theoretical value. That is, The actual velocity distribution according to the position in the interface system was obtained through a fifth-order polynomial fitting algorithm.

[0099] Meanwhile, the position r and momentum p can be expressed as in the following mathematical expressions 3 and 4, respectively.

[0100]

[0101]

[0102] In the above mathematical expression 4, s and Ps are -Items related to the Hoover thermostat can be expressed by the following mathematical expressions 5 and 6.

[0103]

[0104]

[0105] In this way, in the interface system, the velocity distribution of polymers is directly fitted to obtain the item. Because of the addition of , a modified p-SLLOD equation is used. Therefore, the accurate actual velocity distribution of the polymers can be obtained and the transition state can be accurately described.

[0106] The present invention calculates (integrates) each MD step using r-RESPA for a modified p-SLLOD equation based on the improved equation of motion described above.

[0107] Figure 8 is a configuration diagram of a simulation device according to an embodiment of the present invention.

[0108] Referring to FIG. 8, the simulation device (100) may include an input module (110), a calculation module (120), a storage module (130), an output module (140), and a simulation re-run module (150).

[0109] The input module (110) may include an input unit (112), a setup unit (114), and a startup unit (116).

[0110] The input unit (112) receives the initial system environment and system structure required for simulation progress by leading the first information storage unit (10) and the second information storage unit (20). The system environment may refer to time, temperature, density, shear flow intensity, simulation time interval, etc., and the initial system structure may refer to information such as the number of polymer chains existing in the system (nmol), the total number of particles (npartcl), the number and length of branches existing in each chain, the number of particles forming the interface (npartcl_uw, bw), the size of the simulation system box (boxleng), and initial position information for each particle.

[0111] The setting unit (114) creates a simulation box based on the information read by the input unit and obtains the values ​​of variables required for the simulation (box volume, reduced mass, sigma, epsilon, shear rate, etc.).

[0112] The starting part (116) calculates initial values ​​such as force and energy for the initial configuration read from the input file.

[0113] The calculation module (120) may include a first calculation unit (122) and a second calculation unit (124).

[0114] In this embodiment, the calculation module (120) The force acting on each atom is calculated using the formula, where refers to a potential function defined according to the distance between atoms, r. In the case of polyethylene polymers, the types of potential functions are the potential between bonded atoms, The potential between nonbonded atoms, It can be divided into two. Here refers to the energy due to stretching, bending, and torsion between atoms connected to each other within a polymer chain (intra-atomic). corresponds to a Lennard-Jones potential function with attractive and repulsive terms depending on the distance between atoms that are not directly connected between polymer chains (inter-atomic).

[0115] To find the force applied to a specific atom, the potential function of that atom must first be calculated. ). In principle, the atoms that affect a specific atom are all other atoms within the simulation box. However, considering all of them is too inefficient, so in most cases, only atoms located within a certain range around a specific atom are considered. Representative methods include the Verlet neighbor list and the Linked cell method. In the present invention, a new method is devised by appropriately combining the two existing methods to further reduce the simulation calculation time.

[0116] Accordingly, the first calculation unit (122) and the second calculation unit (124) of the present embodiment can operate as follows.

[0117] The first calculation unit (122) performs the role of performing a calculation process that obtains acceleration, velocity, and position based on force while numerically calculating Newton's equation of motion (F=ma) for a sufficiently small time unit (dt) over time, and it is particularly important to accurately model and calculate the force between atoms.

[0118] Specifically, in the case of a polyethylene polymer chain, it is composed of two elements, C and H, and since the H element is much smaller than the C element, it is located at both ends and in the middle of the polymer chain. , The TraPPE (Transferable Potentials for Phase Equilibria) united atom potential model is applied, which considers each unit as an interaction site. Accordingly, the united atoms (united atoms, Or ) between the forces, To find the potential, First, it must be calculated. In the case of the widely used Lennard-Jones potential, the potential value becomes very small when the distance between atoms exceeds a certain distance (cut-off distance; rcut), so it can be ignored. In other words, the potential for a specific atom is calculated by considering only the atoms within the radius rcut of that atom. However, since the positions of atoms continue to change as the actual simulation progresses, atoms within a range slightly larger than rcut from a specific atom (neighbor) are also considered. For this purpose, the Verlet neighbor list and the linked cell method are representatively used. In the present invention, a new method designed based on the two existing methods was used to drastically reduce the simulation calculation time. In addition, p-SLLOD, which is an algorithm that most accurately solves Newton's equations of motion for a nonequilibrium state given an external flow field, such as the plane shear flow applied in this example, was applied, and the r-RESPA (reversible REference System Propagation Algorithm) multiple time scale method was also applied for efficient simulation.

[0119] This first calculation unit (122) can calculate the position and velocity information of the polymer chain.

[0120] The second calculation unit (124) calculates physical characteristics using the position and velocity information calculated by the first calculation unit (122). For example, it can calculate various structural / dynamic properties such as the size of the polymer (radius of gyration), degree of slip, velocity profile, conformation tensor, and alignment angle.

[0121] The storage module (130) calculates the physical characteristic information calculated by the second calculation unit (122).

[0122] The output module (140) performs a function of outputting physical characteristic information. In particular, the output module can be configured to directly observe the movement of polymer chains through a visualization program (e.g., VMD, PyMOL, etc.) (142).

[0123] The simulation rerun module (150) reruns the simulation based on the necessary information stored according to the rules (interval) set in the input unit (112) when the simulation process is stopped. That is, if the simulation is stopped due to a sudden power outage or lack of computing resources during the simulation, the simulation can be restarted. In this case, the simulation rerun can be restarted from the beginning of the simulation or from the point where the simulation was stopped.

[0124]

[0125] Figure 9 is a flowchart explaining a simulation method according to an embodiment of the present invention.

[0126] The input unit (112) reads and receives the initial system environment information stored in the first information storage unit (10) and the initial system structure information stored in the second information storage unit (20) (S100). The initial system environment information may be time, temperature, density, shear flow intensity, simulation time interval, etc. In addition, the initial system structure information may be the number of molecular chains (nmol), the total number of particles (npartcl), the number and length of branches existing in each chain, the number of particles forming the interface (npartcl_uw, bw), the size of the simulation system box (boxleng), initial position information for each particle, etc.

[0127] Then, based on the input information, information required for molecular dynamics simulation of polyethylene melt is acquired (S110). Here, information acquisition can be achieved by calculating information required for simulation, such as box volume, reduced mass, sigma, epsilon, force, shear rate, etc. Additionally, compiled files and files of the first information storage unit (10) and the second information storage unit (20) can be collected into a single directory to generate an executable file.

[0128] Afterwards, a simulation is performed (S120). In the simulation, a first calculation unit (122) applies r-RESPA (reversible-REference System Propagation Algorithm) to the p-SLLOD equation to calculate the position and velocity information of polyethylene melt chains (S122). Thereafter, a second calculation unit (124) uses the position and velocity information to calculate various structural / dynamic properties, such as the radius of gyration of the polymer, the degree of slip, the velocity profile, the conformation tensor, and the alignment angle (S124).

[0129] Meanwhile, during simulation execution, errors that cause the simulation to stop may occur. In this case, even if the error is later recovered, the simulation must be restarted from the beginning. However, the present invention has a simulation rerun module that monitors whether the simulation has stopped and, if so, stores system information about the last calculated time so that the simulation can be restarted from the point where it stopped. This eliminates the need to restart the simulation from the beginning due to a simulation error.

[0130] Meanwhile, the simulated results are calculated at specified time units (e.g., 10 -12 The information stored in the storage module (130) can be stored (S130). And the information stored in the storage module (130) can be provided for the user to check (S140). At this time, it is also possible to directly observe the movement of the polymer chain through a visualization program (e.g., VMD, PyMOL, etc.) (142).

[0131]

[0132] As described above, the present invention can perform strict and accurate simulations of various causes affecting polymer properties by calculating (integrating) each MD step using r-RESPA in the improved p-SLLOD equation by applying an item obtained directly through fifth-order polynomial fitting of the actual velocity distribution in the interface system.

[0133] While the present invention has been described with reference to the illustrated embodiments as described above, these are merely exemplary, and it will be apparent to those skilled in the art that various modifications, changes, and equivalent other embodiments are possible without departing from the spirit and scope of the present invention. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

[0134] It can be used to invent software for simulating molecular dynamics in fields such as polymer rheology.

Claims

1. Input module that receives information required for molecular dynamics simulation of polymers; A calculation module that calculates properties for a polymer by performing molecular dynamics simulation while applying r-RESPA (reversible Reference System Propagation Algorithm) to the p-SLLOD equation based on the above input information; A storage module that stores the calculated properties in a specified time unit; and A polymer melt simulation device characterized by comprising an output module that outputs the stored attribute information.

2. In paragraph 1, The above p-SLLOD equation is as follows, and the equation above is to keep the simulation temperature constant. -A simulation device for polymer melts, in which a Hoover thermostat is applied. Here, the above refers to the actual nonlinear velocity distribution of polymers directly calculated by polynomial fitting in the interfacial system.

3. In paragraph 1, The above calculation module, A first calculation unit for calculating position and velocity information of a polymer chain; and A simulation device for a polymer melt, comprising a second calculation unit that calculates structural and dynamic properties of the polymer using the position and velocity information.

4. In paragraph 1, The above calculation module, A simulation device for polymer melts, which calculates using a Lennard-Jones potential function with attractive and repulsive terms depending on the distance between atoms, and a Linked cell and Neighbor list method that consider only neighbor atoms depending on the distance between atoms.

5. In paragraph 1, The above output module, A simulation device for polymer melts that allows observation of the movement of polymer chains through a visualization program.

6. In paragraph 1, Further comprising a simulation re-run module that performs whether to re-run the above simulation, The above simulation re-run module is, A polymer melt simulation device that stores system information about the last calculated time so that the simulation can be restarted from the point where the simulation was stopped if the simulation is stopped.

7. In paragraph 1, The information required for the above simulation is: Initial system environment information including time, temperature, density, shear flow intensity, and simulation time interval; and A simulation device for a polymer melt, comprising initial system structure information including the number of molecular chains (nmol), the total number of particles (npartcl), the number and length of branches present in each chain, the number of particles forming an interface (npartcl_uw, bw), the size of the simulation system box (boxleng), and initial position information for each particle.

8. Acquisition step for acquiring information required for molecular dynamics simulation of polymers; A calculation step for calculating properties of a polymer by performing a molecular dynamics simulation based on the information obtained above; and A simulation method for a polymer melt, characterized in that it includes a storage step of storing the calculated properties in a specified time unit.

9. In paragraph 8, The above calculation steps are: A simulation method for polymer melts that calculates (integrates) each MD step using the r-RESPA (reversible Reference System Propagation Algorithm) in the p-SLLOD equation for the current simulation.

10. In paragraph 8, The above calculation step calculates the properties using the following equation, and when calculating the properties, the simulation temperature is kept constant. -A simulation method for polymer melts using a Hoover thermostat. Here, the above refers to the actual nonlinear velocity distribution of polymers directly calculated by polynomial fitting in the interfacial system.

11. In paragraph 8, The above calculation steps are: A first calculation step for calculating the position and velocity information of the polymer chain; and A simulation method for a polymer melt, comprising a second calculation step of calculating structural and dynamic properties of the polymer using the position and velocity information.

12. In paragraph 8, The above calculation steps are: A simulation method for polymer melts using the Lennard-Jones potential function with attractive and repulsive terms depending on the distance between atoms.

13. In paragraph 8, Before the above acquisition step, A simulation method for a polymer melt, further comprising an input step for receiving information on an initial system environment and initial system structure required for performing a simulation.

14. In paragraph 13, The above initial system environment information is: Includes time, temperature, density, shear flow intensity, and simulation time interval, The above initial system structure information is: A simulation method for a polymer melt, including the number of molecular chains (nmol), the total number of particles (npartcl), the number and length of branches existing in each chain, the number of particles forming an interface (npartcl_uw, bw), the size of the simulation system box (boxleng), and initial position information for each particle.

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