[lammps-users] fix press/berendsen error

Dear lammps users,

I am trying to do npt by using langevin simulation. Below is a core part of my simulation. When running this script, error says " Non-numeric atom coords - simulation unstable". I couldn’t get which one is not correct. Can anyone give me a hand?

With my best regards

--------- core part of the input script ----------
timestep 0.1
fix fNVE all nve
thermo 10
thermo_style custom step pe

minimize 1.0e-6 1.0e-7 10000 100000
min_style cg

unfix fNVE

compute cTEMP all temp
compute cPRES all pressure cTEMP
fix fTEMP all ave/time 1 {thermoFreq} {thermoFreq} c_cTEMP ave one
fix fPRES all ave/time 1 {thermoFreq} {thermoFreq} c_cPRES ave one

reset_timestep 0
timestep ${dt}

fix fNVE all nve
fix fLANG all langevin {t} {t} {taut} 30291 fix fBRS all press/berendsen iso 1.0 1.0 {taup}

thermo ${thermoFreq}
thermo_style custom step etotal ke pe f_fPRES vol f_fTEMP density ecoul evdwl ebond

dump lammpstrj all custom {dumpFreq} {dumpPath} id mol type x y z ix iy iz

restart {rstFreq} {rstPath}

run ${Nsteps}
------------------------------- end of the input script -----------------------------------

I cannot determine what you are simulating and what the Pdamp factor of berendsen barostat is based on the imformation you provide. But the unstable simulation may require the adjustment of Pdamp. Here is the reply that axel once gave me, hope it will be helpful to you.

“the berendsen barostat will not be stable for any choice of Pdamp for any system. if it is chosen too short, then you get too large volume fluctuations and those will lead to numerical instabilities due to a resonance between the pressure fluctuations and the rescaling from the fix”