I want to do basic equilibrium simulation of ethane and compare my results with experimental or theoretical thermodynamic properties. But my results cannot match the experimental data well.
For example, when pressure=0.5Mpa, temperature=300K, the density of ethane should be 6.26kg/m3, but my result is about 5.6kg/m3; when pressure=0.1Mpa, temperature=300K, the density of ethane should be 1.2144kg/m3, but my result is about 1.11kg/m3.
How to do simple gas equilibrium simulation to get those correct thermodynamic properties like density? Is there any example I can refer to? My input file and molecule template are shown below:
Input file:
ethane Equilibration
log log.eth
units real
molecule ETH c2h6.data
#atom_style template ETH
atom_style full
bond_style harmonic
boundary p p p
lattice fcc 54.49
region box block 0 10 0 10 0 10
create_box 1 box bond/types 1 extra/bond/per/atom 1
mass 1 15.035
create_atoms 0 box mol ETH 19871010
#create_atoms 0 random 540 1111 NULL mol ETH 19871010
velocity all create 300 482748
pair_style lj/cut 14.0
pair_coeff 1 1 0.1946 3.750
bond_coeff 1 95.806 1.54
special_bonds lj 0.0 0.0 0.0
minimize 1.0e-5 1.0e-7 1000 10000
fix fxnpt all npt temp 300.00 300.00 100.0 iso 4.98 4.98 1000
dump id all atom 500 dump.Equeth.lammpstrj
timestep 1.0
thermo_style custom step temp press etotal density vol
thermo 500
run 2000000
molecule template file:
LAMMPS Description
2 atoms
1 bonds
0 angles
0 dihedrals
0 impropers
Coords
1 -0.77 0.0 0.0
2 0.77 0.0 0.0
Types
1 1
2 1
Charges
1 0.0
2 0.0
Bonds
1 1 1 2
Special Bond Counts
1 1 0 0
2 1 0 0
Special Bonds
1 2
2 1
Thank you!!!
eth.in (791 Bytes)
c2h6.data (321 Bytes)