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Re: [lammps-users] Error during applying "npt" command.
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Re: [lammps-users] Error during applying "npt" command.


From: Axel Kohlmeyer <akohlmey@...24...>
Date: Mon, 4 Dec 2017 03:31:02 -0500



On Mon, Dec 4, 2017 at 12:51 AM, swarnimaa B. via lammps-users <lammps-users@lists.sourceforge.net> wrote:
Dear Steve Sir,

I am running a simulation for graphene-water system. I have applied "npt" ensemble in my simulation. But I am getting an error i.e. "Non-numeric pressure - simulation unstable". I checked documentation for this, even went through the lammps mailing list also. But still I am unable to resolve this error. Although there is no any issue in my model geometry as I checked. I am facing this problem only in 'npt' command.
Please Sir help me out of this. I would always be thankful to you.

​you posted the exact same input, but also accompanies with some LAMMPS output​, about two weeks ago.
at the time, your energies and pressures during minimization were *extremely* high, first firs positive, then negative.
this is a clear sign of a bad geometry and/or force field settings.

​there is no additional information here. and thus no indication that you have made any progress. however, your fix npt error indicates, that you still have a bad geometry.
that are also obvious mistakes in this input beyond the npt run.

with no more specific information or indication, that you actually have improved your setup, there is no way to help you.

GI-GO,
   axel.

 

Here is my lammps input script.

units           real
dimension       3
boundary        p p p
atom_style      full
#atom_modify    map array
neigh_modify    delay 0 every 1 check yes
processors      * * *

# atom definition:
read_data     graphene.data

###############################################
# group definition:
group           oxygen type 1
group           hydrogens type 2
group           fluidmols type 1 2
group           potassium type 3
group           chloride type 4
group           ions type 3 4
group           graphene type 5
group           solutions type 1 2 3 4 5
#################################################
# force fields
variable        rcF equal 12.0
pair_style      lj/cut/coul/long  ${rcF} ${rcF}
pair_coeff      1 1  0.15539   3.1656      
pair_coeff      2 2  0.0       0.0        
pair_coeff      3 3  0.43      2.84        
pair_coeff      4 4  0.0128    4.83        
#----------Graphene-Water interaction------------------
pair_coeff      5 5   0.06844   3.407       
pair_coeff      1 5   0.1039    3.372       
pair_coeff      2 5   0.0256    2.640       
pair_modify    mix arithmetic
############################################
kspace_style    pppm 1e-05
dielectric          1.0
bond_style      harmonic
bond_coeff      1 450.0 1.0
angle_style     harmonic
angle_coeff     1 100.0 109.47

# minimization
min_style       sd
minimize        1.0e-4 1.0e-5 1000 10000
###############################################
reset_timestep   0
timestep            1.0
compute            fluidtemp solutions temp
velocity             solutions create 300 2000 dist gaussian temp fluidtemp mom yes rot yes units box
######################################################################################
fix   1 fluidmols shake 0.0001 20 0 b 1 a 1
fix   GD ions flow/gauss 0 0 1 energy yes
#################################################################
fix   fxnpt all npt temp 300.0 300.0 100.0 iso 1.0 1.0 1000.0
run   10000
################################################
fix   fxnvt solutions nvt temp 300 300 100.0
run   10000
#########################################
fix_modify fm temp lammpsTemp press lammpsPress
#####################################################
fix   ef all efield 0.0 0.0 0.1
dump  2 ions dcd 1000 ions.dcd
dump  3 all custom 5000 system.lammpstrj id type x y z
################################################################################################
reset_timestep    0
thermo               50
thermo_style    multi
run                  15000


Thanks & Regards,
Swarnimaa




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--
Dr. Axel Kohlmeyer  akohlmey@...12...24...  http://goo.gl/1wk0
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.