Hello everyone,
I am trying to simulate a system where a polymer is confined between two walls and the top wall is moving is X direction with a velocity 0.0001 A/fs, bottom wall is fixed.
I am using NVE/limit ensemble with temperature rescale. Any other ( like only NVE ) gives error.
Because of temperature rescale the polymer temperature is maintained at 330 K but the temeprature of individual vertical layers ( regions) are very high ~ 2000 K and more.
Experiemntally reported value is about 300 - 700 K.
Can anyone please tell me what’s wrong with my temperature set up, or how can I get a more realistic value ?
I am running the simulation with 1 fs time step for about 1 ns.
Thank you very much for suggestion.
Mani
My input file:
clear
units real
boundary p p s
#Defining the different potential types
pair_style lj/cut/coul/cut 12 12
#kspace_style pppm 0.0001
atom_style full
angle_style harmonic
bond_style harmonic
dihedral_style harmonic
improper_style cvff
#Data Reading and neighbouring information
neighbor 2.0 bin
neigh_modify every 1 delay 0 check yes one 200000 page 2000000
#read_data Layer-n-mw3000r.lammps05
read_restart restart_ab
pair_modify shift yes mix arithmetic
group fluid molecule <> 2 25
group additive molecule <> 2 5
group lube molecule <> 5 25
region 1 block -INF INF -INF INF 0.0 10.5 units box
region 2 block -INF INF -INF INF 41.5 52.5 units box
region 3 block -INF INF -INF INF 10.5 12.5 units box
…
…
group base region 1
group top region 2
group nomove union base top
group fluid subtract all nomove
fix freeze1 top setforce 0.0 0.0 0.0
fix freeze2 base setforce 0.0 0.0 0.0
compute mobile all temp
compute_modify mobile dynamic yes
fix 1 all nve/limit 0.5
fix 11 all temp/rescale 100 300.0 300.0 50.0 0.5
fix_modify 11 temp mobile
velocity top set 0.0001 0.0 0.0 sum no units box
compute atomtemp1 base temp/region 1
…
…
thermo_style custom step temp etotal press ke pe c_pe c_eng1 c_eng2 …
log log_ab
dump 1 all custom 1000 trj_ab id mol type q xu yu zu fx fy fz c_peratom
dump 3 all xyz 100 dump.za58-2700mod.sdnve3.xyz
thermo 100
thermo_modify temp mobile
timestep 1.0
run 250000
write_restart restart_ab