I am a newbie to lammps software and I would like to ask some lammps questions, I have most been learning to use the bond/swap command of lammps to describe Vitrimer materials and I am having problems using this command.
I built the crosslinked polymer using the PCFF force field of the MS software, then converted it to a data file and imported it into lammps, then trying to build the Vitrimer using the form of the bond/swap command case 2 in the lammps manual, I put the atoms at both ends of the dynamic bond into a group based on the type type, and ran the program, and found out through the output that the The program tries many times to swap but has not successfully executed a single swap, would like to ask what is the reason for this?
Here’s my .in file:
###初始化
units real #timestep 1 fs
boundary p p p
atom_style full
###设置势能
bond_style class2
angle_style class2
dihedral_style class2
pair_style lj/class2/coul/long 5
improper_style class2
kspace_style ewald 1.0e-4 #文件带电荷所以需要定义一个KSspace命令
newton off off
#--------模型读取-------#
read_data A.data #读取MS建立的模型
dihedral_style none
improper_style none
special_bonds lj 0.0 1.0 1.0
#-------设置邻居参数-------#
neighbor 2.0 bin #截断距离2.0
neigh_modify every 1 delay 0 check yes
group A1 type 2 4
#-----------------------平衡态分子模拟------------------------------#
#-----------温度初始化--------#
velocity all create 500 3256 dist gaussian
#-------npt条件下弛豫-------#
reset_timestep 0 #起始步数归零
fix 1 all npt temp 500 500 50 iso 0 0 1000 #npt弛豫。起始终止温度500-500，波动温度50。起始终止压力0，波动压力1000。
fix 2 A1 bond/swap 50 0.5 4 52525
compute fix_2 all temp
dump 1 all custom 1000 1.xyz id type x y z #输出npt弛豫下所有原子的xyz坐标。
thermo 1000 #1000步输出一次
thermo_style custom step time temp f_2[1]
run 200000
unfix 1
unfix 2
undump 1
write_data DT.data