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


From: "swarnimaa B." <swarnimaa39@...16...>
Date: Mon, 4 Dec 2017 05:51:07 +0000 (UTC)

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.

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