LAMMPS WWW Site - LAMMPS Documentation - LAMMPS Mailing List Archives
[lammps-users] Density of methanol
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[lammps-users] Density of methanol


From: 노승효<mozoningen@...1911...>
Date: Thu, 17 Aug 2017 23:15:06 +0900

To lammps users,

 

I am testing the density of methanol using a given example of LAMMPS software (~/LAMMPS/Examples/dreading/)

 

It is known that the density of methanol is ~0.792 g/cm3.

 

The initial density of methanol example was 0.457 g/cm3 but the density is lower, showing the enlarged unitcell.

 

How can I get reasonable vlaue (~0.792 g/cm3)?

 

## results##

 Step Temp TotEng PotEng KinEng Lx Ly Lz Press Density
       0       298.15    12308.081    3094.6323    9213.4485     59.99067     57.38448     58.40913    1781.0418    0.4572555
    1000    290.58157    19927.153    10947.585    8979.5683    70.096033    67.050833    68.248084    -92.74926   0.28663535
    2000    305.64025    21030.387    11585.475    9444.9127    81.307743     77.77547    79.164219    60.844666    0.1836599
    3000    302.94026     21826.71    12465.233    9361.4774    93.059138    89.016346    90.605811    97.386573   0.12249913

 

## input script ##

 units           real
atom_style      full
boundary        p p p
dielectric      1
special_bonds   lj/coul 0.0 0.0 1.0

pair_style      hybrid/overlay hbond/dreiding/lj 2 6 6.5 90 lj/cut/coul/long 8.50000  11.5
bond_style      harmonic 
angle_style     harmonic 
dihedral_style  harmonic
improper_style  none
kspace_style    pppm 0.001  

read_data       data.dreiding

replicate 3 3 3

pair_coeff      1    1    lj/cut/coul/long        0.015200000256300         2.846421344984478 
pair_coeff      1    2    lj/cut/coul/long        0.001232882795416         2.846421344984478
pair_coeff      1    3    lj/cut/coul/long        0.038019995160237         3.159705878878677
pair_coeff      1    4    lj/cut/coul/long        0.038139744011598         2.939787518071103
pair_coeff      2    2    lj/cut/coul/long     9.99999974737875e-05         2.846421344984478
pair_coeff      2    3    lj/cut/coul/long        0.003083828758188         3.159705878878677
pair_coeff      2    4    lj/cut/coul/long        0.003093541672406         2.939787518071103
pair_coeff      3    3    lj/cut/coul/long        0.095100000500679         3.472990412772877
pair_coeff      3    4    lj/cut/coul/long        0.095399530150179         3.253072051965302
pair_coeff      4    4    lj/cut/coul/long        0.095700003206730         3.033153691157727
pair_coeff      4    4    hbond/dreiding/lj 2 i 0.4000E+01 2.750000000000000 4
pair_modify     mix arithmetic
neighbor        2.0 multi
neigh_modify    every 2 delay 4 check yes
variable        input index in.ch3oh.box.dreiding
variable        sname index ch3oh.box.dreiding

compute   hb all pair hbond/dreiding/lj
variable    C_hbond equal c_hb[1] #number hbonds
variable    E_hbond equal c_hb[2] #hbond energy
#thermo_style   custom etotal ke temp pe ebond eangle edihed eimp evdwl ecoul elong v_E_hbond v_C_hbond press vol
#thermo_modify  line multi format float %14.6f

 

# Output
thermo         1000
thermo_style   custom step temp etotal pe ke lx ly lz press density

dump myOvito all custom 1000 dump.ovito.* id type xs ys zs

 

################### NPT
timestep 1
velocity       all create 298.15 4928459 rot yes mom yes dist gaussian
#fix ensemble_press all press/berendsen iso 1.0 1.0 1000.0
fix   fxnpt all npt temp 300.0 300.0 100.0 iso 1.0 1.0 100.0
run 100000
unfix fxnpt
#unfix ensemble_press
reset_timestep 0