I was given this could that was initially fix NVT but I need to change values to where pressure is constant to see volumetric changes. When i run this code I run into an error: ERROR: Must not have multiple fixes change box parameter x (…/domain.cpp:168)
Last command: run 10000
should i add another y parameter for my fix NPT command line?
LAMMPS Input Script for Bulk Water
units metal
newton on
dimension 3
boundary p p p
atom_style full
bond_style harmonic
angle_style harmonic
variable T equal 300.0 # run temperature
variable Tinit equal 320.0 # equilibration temperature
variable V equal vol
variable dt equal 0.001
variable P equal press
variable p equal 20 # correlation length
variable s equal 5 # sample interval
variable d equal $p*$s # dump interval
convert from LAMMPS metal units to SI
variable kB equal 1.3806504e-23 # [J/K] Boltzmann
variable bar2Pa equal 100000.0
variable A2m equal 1.0e-10
variable ps2s equal 1.0e-12
variable convert equal {bar2Pa}*{bar2Pa}{ps2s}*{A2m}{A2m}*{A2m}
setup problem
read_data bulk_water_1.dat
run_style verlet
group wat type 1 2
group oxy type 1
Potential Calculation
pair_style hybrid lj/cut/tip4p/long 1 2 1 1 0.1577 10.0 #lj/cut 10.0 # tersoff
kspace_style pppm/tip4p 1.0e-4
pair_coeff * * tersoff BNC.tersoff NULL NULL
pair_coeff 1 1 lj/cut/tip4p/long 0.009066589 3.1688000
pair_coeff 1 2 lj/cut/tip4p/long 0.0 0.0
pair_coeff 2 2 lj/cut/tip4p/long 0.0 0.0
bond_coeff 1 0 0.9572
angle_coeff 1 0 104.52
neighbor 2.0 bin
neigh_modify every 1 check yes
timestep ${dt}
thermo $d
#----------------------------Energy minimization----------------------------
fix 1 all box/relax iso 1.0 dilate partial
min_style cg ## minimization (using CG method)
minimize 1.0e-10 1.0e-10 1000 1000
unfix 1
#----------------------------System relaxation------------------------------
fix WatShake wat shake 1e-4 20 0 b 1 a 1
timestep 0.5
velocity all create 300.0 54391 mom yes rot yes dist gaussian #temp Tpt bias yes
#fix npt1 wI npt temp $T $T 0.0001 x 1.0 1.0 0.1 y 1.0 1.0 0.1
thermo 1000
thermo_style custom step cpu temp press ke pe etotal vol density #c_TR c_TM
dump 2dump all atom 1000 Trans_NPT_output.lammpstrj
run 20000
unfix npt1
undump 2dump
group WG type 1 2 3
fix WatShake wat shake 1e-4 20 0 b 1 a 1
#-----------------------equilibration and thermalization----------------------
velocity all create {Tinit} 102486 mom yes rot yes dist gaussian
fix NPT all npt temp {Tinit} ${Tinit} 100 x 1.0 1.0 1000.0
run 20000
#----------------------viscosity calculation, switch to NVE if desired----------
velocity all create $T 102486 mom yes rot yes dist gaussian
fix NPT all npt temp $T $T 100 x 1.0 1.0 1000.0
#unfix NVT
#fix NVE all nve
reset_timestep 0
variable pxy equal pxy
variable pxz equal pxz
variable pyz equal pyz
fix SS all ave/correlate $s $p d &
v_pxy v_pxz v_pyz type auto file S0S2t.dat ave running
variable scale equal {convert}/(${kB}$T)$V*s*{dt}
variable v11 equal trap(f_SS[3]){scale}
variable v22 equal trap(f_SS[4])*{scale}
variable v33 equal trap(f_SS[5])${scale}
thermo_style custom step temp press v_pxy v_pxz v_pyz v_v11 v_v22 v_v33
restart 1000000 Water_GF_NVT.restart
run 5000000
variable v equal (v_v11+v_v22+v_v33)/3.0
variable ndens equal count(all)/vol
print “average viscosity: $v [Pa.s] @ T K, {ndens} atoms/A^3”