准备工作

LAMMPS + USER-REAXC + MOLECULE packages

安装msi2lmp

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安装完成在src出现msi2lmp.exe,用于将从Materials Studio等软件生成的模型中得到lammps需要的data文件。

data文件

在Materials Studio中建模

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在Modules→Forcite→Calculation中设置势函数:

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不需要Run,直接关闭窗口。

导出成car格式:

会生成car和mdf两个文件。

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用msi2lmp转换:

./msi2lmp.exe graphite -p o -frc cvff -i -n > data.graphite

生成data.graphite和graphite.data两个文件,其中graphite.data就是需要的文件。

LAMMPS data file. msi2lmp v3.9.9 / 05 Nov 2018 / CGCMM for graphite

    100 atoms
    150 bonds
    300 angles
    600 dihedrals
    100 impropers

   1 atom types
   1 bond types
   1 angle types
   1 dihedral types
   1 improper types

    -6.150000000     6.150000000 xlo xhi
    -5.326056233     5.326056233 ylo yhi
    -3.400000000     3.400000000 zlo zhi
    -6.150000000     0.000000000     0.000000000 xy xz yz

Masses

   1   12.0107 # xx



Atoms # full

      1      1   1  0.000000     0.000000000     0.000000000     1.700000000   0   0   0 # xx
      2      1   1  0.000000     0.000000000    -0.000000000    -1.700000000   0   0   1 # xx
......

势文件

examples→reax→FC→ffield.reax.FC

input脚本

boundary     p p p
units        real #用reaxff势需要选real单位
atom_style   full #看生成的data文件里写了要用full,这需要安装MOLECULE package

read_data    graphite.data

#mass       *   12.0107

pair_style  reax/c NULL #要用reaxff势,需要安装USER-REAXC
pair_coeff  * * ffield.reax.FC C
neighbor     2. bin #截断半径,与单位有关,详细见附录
neigh_modify    every 10 delay 0 check no #截断半径的刷新频率

#Langevin random seed
variable     dt equal 2e-3
variable     r  equal 57085
variable     T  equal 300
variable     dT equal "v_dt * 100"

# initialize
velocity     all create $T 28459 rot yes dist gaussian mom yes
fix          1 all langevin $T $T ${dT} 73504 zero yes
fix     2 all nve
fix             3 all qeq/reax 1 0.0 10.0 1e-6 reax/c #用reaxff必须要有电荷守恒条件

timestep    0.25

#dump    1 all movie 10 reaxff.mp4 type type
dump   2 all xyz 10 dump.reaxff.xyz

run                 1000

运行结果

附录

截断半径

0.3 bin for units = lj, skin = 0.3 sigma

2.0 bin for units = real or metal, skin = 2.0 Angstroms

0.001 bin for units = si, skin = 0.001 meters = 1.0 mm

0.1 bin for units = cgs, skin = 0.1 cm = 1.0 mm


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