Large pressure fluctuations in NPT ensemble for polymer melt

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1

Hi all,

I am simulating linear polymer chains in NPT ensemble, but the pressure fluctuates from 0.2 to 1.2 at target pressure P=1.0. Can i request to help me to resolve the problem. The input script is given below:

units lj
atom_style bond
special_bonds fene

read_data data.chain

neighbor 0.4 bin
neigh_modify every 1 delay 1

bond_style fene
bond_coeff 1 30.0 1.5 1.0 1.0

pair_style lj/cut 1.12
pair_modify shift yes
pair_coeff 1 1 1.0 1.0 1.12

fix 2 all npt temp 1.0 1.0 \(100\.0\*dt\) iso 5\.5 5\.5 (8000.0*dt)
dump 3 all custom 100 crd.xyz.* id type xu yu zu ix iy iz vx vy vz

thermo 1000
timestep 0.010

restart 100000 poly.restart
run 1000000

Thanks in anticipation!!

~Jalim

2

Actually, the pressure is given in input as 1.0 1.0 and not 5.5.

fix 2 all npt temp 1.0 1.0 \(100\.0\*dt\) iso 5\.5 5\.5 (8000.0*dt)

3

please see the mailing list archives for the many, many discussions on pressure fluctuations.

axel.