Dear All,
I want to simulate amorphous silica for which I will be melting and quenching the amorphous phase with the BKS potential. I am performing melting at 5000 K. Then I want to quench the system from 5000 K to 300K at rate of 5K/ps. However, when I perform melting process at 5000K, I see the temperature of the system is not fixed to 5000K but keep on increasing. I performed simulation with NVE ensemble and then also tested with fix NVT and fix NPT both. But for all the cases the temperature of the system was increasing. My system contains 795 atoms (265 SiO2 molecules) that were randomly placed in a box of 20A20A30A. My Lammps input file and datafile are written below … Does anybody have any idea about what this problem may be due to?
With thanks and regards,
Pooja
Lammps input file
dimension 3
boundary p p p
units real
atom_style charge
neighbor 0.3 bin
neigh_modify delay 1
read_data FilledConfig.data
Buck potentials
kspace_style pppm 1.0e-4
pair_style buck/coul/long 8 10
Si type 1, O type 2
pair_coeff 1 1 0.00000 0.100000 0.000000
pair_coeff 1 2 415172.94230 0.205205 3079.435324
pair_coeff 2 2 32025.59145 0.362319 4035.561250
initial velocities
velocity all create 5000.0 4928459
#fix 1 all nve
#fix 1 all nvt temp 5000.0 5000.0 100.0
#fix 2 all npt temp 5000.0 5000.0 100.0 iso 0.00 0.00 1000.0
fix 2 all npt temp 5000.0 5000.0 100.0 iso 1.00 1.00 1000.0
Run
timestep 0.0005# Custom data file for mixture of, SiO2,
thermo 100
thermo_modify temp new
dump 6 all custom 1000 Bk5silica.dump id type x y z
restart 10000 restart
run 1000000
… Datafile …
795 atoms
2 atom types
0.00000000000000 27.00000000000000 xlo xhi
0.00000000000000 27.00000000000000 ylo yhi
0.00000000000000 37.00000000000000 zlo zhi
Masses
1 28.0855000000000
2 15.9994000000000
Atoms
1 1 2.40000000000000 21.19574979863687 26.56314348998866 16.60392077187158
2 2 -1.20000000000000 20.92168213846226 25.53602206331959 15.51052093332094
3 2 -1.20000000000000 21.47366081769066 27.59632008729189 17.69062596179387
4 1 2.40000000000000 4.03179762537331 10.97965995043920 7.14349606133526
5 2 -1.20000000000000 3.65206065147185 10.83498298398472 8.61335425873001
6 2 -1.20000000000000 793 1 2.40000000000000 4.71131037495489 19.71224239165641 24.08558656679686
…
…
793 1 2.40000000000000 4.71131037495489 19.71224239165641 24.08558656679686
794 2 -1.20000000000000 4.31561499933014 20.34039317191318 22.75349554836349
795 2 -1.20000000000000 5.10559026902073 19.09271841574135 25.42213061542843
4.42100242879972 11.12482182623187 5.67616370759368