Hello, Dear lammps user,
I wrote a file about polymer (PETG) and then get it in equilibrium and tensile it. But even I run the simulation with long enough time, the bonds will never break(which should be broken actually). Through ovito or vmd I can see that the distance between bond atoms is far enough but the strain stress curve shows that the bonds are not broken.
Here is my in file:
variable project index “PETG” # project name
variable project index “petg” # project name
variable source index …/build # data directory
variable params index …/build # parameter directory
variable temperature index 300 # system temperature
variable tdamp index 100 # temperature damping
variable dielectric index 1 # medium dielectric
variable kappa index 4 # electrostatics kappa
variable cutoff index 9.5 # standard cutoff
variable charge_cutoff index 9.5 # charge cutoff
variable precision index 0.001 # kspace precision
variable lseed index 723853 # langevin seed
variable vseed index 1486234 # velocity init seed
variable tequil index 50000 # equilibration time
variable trun index 10000000 # run time
variable frestart index 0 # 0: equil, 1: restart
variable dtrestart index 100000 # delta restart time
variable dtdump index 100000 # delta dump time
variable dtthermo index 1000 # delta thermo time
variable timestep index 0.5 # integration time step
variable tfreq index 10 # profile sampling freq
variable nsample index 1000 # profile conf sampling
variable dtime equal {tfreq}*{nsample} # profile dtime
variable restart index {params}/{project}.restart
New Variables for output
variable p1 equal “time”
variable p2 equal “vol”
variable p3 equal “pe”
variable p4 equal “temp”
variable p5 equal “etotal”
variable p6 equal “density”
variable p7 equal “mol”
if “${frestart} != 0” then &
“variable data index ${restart}” &
else &
“variable data index ${project}.data” &
LAMMPS atomistic input script
echo screen
units real
atom_style full
Interaction potential definition
pair_style lj/class2/coul/long {cutoff} {charge_cutoff}
bond_style harmonic
special_bonds lj/coul 0 0 1
if “{frestart} != 0" then "read_restart {data}” else “read_data ${data}”
include ${project}.params
Integration conditions (check)
timestep ${timestep}
kspace_style pppm/cg ${precision}
dielectric ${dielectric}
fix mom all momentum 100 linear 1 1 1 angular
Set thermo output
thermo 1000
thermo_style custom step pe etotal temp time vol density
Calculate the mean squared displacement for Multiple chunks of atoms
compute cc1 all chunk/atom molecule
compute msd1 all msd/chunk cc1
#fix msd1 all ave/time 1000 1 1000 c_msd1[*] file tmp.out mode vector