Dear users,
I am trying to heat and melt a silica system of 648 atoms using the appended code. Some sample results which I have appended beneath the code showed that the pressure is fluctuating between large positive and negative values. I would like to know whether this is normal?
Also, by running for more than 70000 time steps, the temperature does not seem to be able to increase to the value I have set in the fix. If any users can spot any issues, kindly advise.
One last question, if I read atomic positions using read_data, is it still necessary to use the “lattice” command? Thank you!
#CODE
buckingham potential with LJ overlay
dimension 3
boundary p p p
units metal
atom_style charge
create geometry
lattice fcc 7.16
read_data silica.DAT
Buck potentials
kspace_style pppm 0.00001
pair_style hybrid/overlay buck/coul/long 8.0 lj/cut 8.0
Si type 1, O type 2
pair_coeff 1 1 buck/coul/long 0.0 0.10 0.0
pair_coeff 1 2 buck/coul/long 18003.7572 0.205205 133.5381
pair_coeff 2 2 buck/coul/long 1388.7730 0.362319 175.0
pair_coeff 1 1 lj/cut 13.2 0.4
pair_coeff 1 2 lj/cut 0.0112 1.35
pair_coeff 2 2 lj/cut 0.000478 2.2
initial velocities
compute new all temp
compute 1 all pe/atom
compute 2 all ke/atom
compute 3 all stress/atom pair
velocity all create 300.0 482748 temp new
fix 1 all nvt temp 300.0 5000.0 100.0
Run
timestep 0.0005
thermo 100
thermo_modify temp new
#Dump format: dump ID group-ID style N file args
dump 1 all custom 100 dump.buck.* id type x y z q vx vy vz c_1 c_2 c_3[1]
run 72000
#SAMPLE RESULTS
Step Temp E_pair E_mol TotEng Press
11100 566.62866 -12503.431 0 -12456.043 -3384.8727
11200 569.63338 -12503.663 0 -12456.023 6149.4496
11300 590.86814 -12505.458 0 -12456.043 988.61351
11400 571.21272 -12503.845 0 -12456.074 1516.7706
11500 584.26853 -12504.951 0 -12456.088 747.02903
11600 571.44698 -12503.906 0 -12456.115 -148.67779
11700 586.252 -12505.139 0 -12456.11 -3314.6251
11800 592.20524 -12505.628 0 -12456.101 -2373.954
11900 582.05867 -12504.742 0 -12456.064 4775.4808
12000 560.06536 -12502.898 0 -12456.059 4125.6407
12100 600.17716 -12506.275 0 -12456.081 -2920.4871
12200 562.03553 -12503.064 0 -12456.061 -1951.4006
12300 572.11208 -12503.889 0 -12456.042 4380.9368
12400 581.77293 -12504.707 0 -12456.052 7449.4511
12500 578.57178 -12504.448 0 -12456.062 -5771.4148
12600 571.13763 -12503.833 0 -12456.068 -2944.7055
12700 568.76238 -12503.59 0 -12456.024 5339.5803
12800 562.81299 -12503.09 0 -12456.022 4550.9351
12900 579.50986 -12504.503 0 -12456.038 -3919.8918
13000 567.32907 -12503.521 0 -12456.074 -2848.9998
13100 560.12176 -12502.879 0 -12456.036 3211.0218
13200 546.95967 -12501.79 0 -12456.047 1970.7405
13300 579.26028 -12504.485 0 -12456.041 1188.4779
13400 548.05406 -12501.901 0 -12456.066 2583.3702
13500 561.68922 -12503.036 0 -12456.061 -7578.3281
13600 580.25763 -12504.571 0 -12456.044 3259.1659
13700 586.25 -12505.049 0 -12456.02 7497.8056
13800 570.17667 -12503.761 0 -12456.077 -3846.4967