Dear Users,
I am having a problem when trying to implement the BKS potential for a-quartz using the Pair-style table command.
My code used to run fine when implementing the BKS potential using the Buck/coul/long pair style.
Now I want to add an additional 24-6 LJ potential on top of the BKS potential so I want to implement these two using a table (No built in 24-6 LJ potential in lammps so cannot use Hybrid overlay command).
The problem is when I use the Pair style table, I lose atoms:
- When not specifying RSQ parameters in the table I lose atoms after about 160 steps
- When specifying RSQ, I lose almost all atoms at the first step.
Temperature and kinetic energy start increasing from the initial 450K (although I run NVT 300K) to 10^12 K before losing atoms.
Pressure is negative at the first step.
- When not specifying RSQ in table, pressure is --9035954.5 (metal units) and steady till the last three steps before losing atoms where it explodes up to +10^13 (metal units)
- When specifying RSQ, I lose atoms after the first step and pressure is -10^11 (metal units).
I used the same parameters to generate my potential and force table in excel as in the Buck/coul/long potential. The same ones that from the original Ban best/Kramer/Van Santen (1990) publication. And I plotted them to double check they looked all good.
Also I tried to refine my table more and more (I am currently using 10000 data point for each pair, ranging from 0.0001A to 10A plus Kspace PPPM 10^-4.
I plotted the potentials using Pair write and they look very good. No problem.
Once again, This code used to be working good and giving good thermal conductivity values when using Pair style buck/coul/long. Here the only thing I did was to replace it by a table.
Here is the input script followed by the first few lines of the Potential table file.
Does anybody know what it is that I am doing wrong. Help would be greatly appreciated.
Thank you very much in advance.
Sincerely,
INPUT SCRIPT
#Initialization############################################################
units metal
dimension 3
boundary p p p
atom_style charge
Atom definition##########################################################
lattice custom 5.4054 &
a1 0.9095 0.0000 0.0000 &
a2 -0.4547 0.7876 0.0000 &
a3 0.0000 0.0000 1.0000 &
basis 0.4697 0.0000 0.0000 basis 0.0000 0.4697 0.6667 basis 0.5303 0.5303 0.3333 basis 0.4135 0.2669 0.1191 basis 0.2669 0.4135 0.5475 basis 0.7331 0.1466 0.7857 basis 0.5865 0.8534 0.2142 basis 0.8534 0.5865 0.4524 basis 0.1466 0.7331 0.8809
region simbox block 0 4 0 4 0 4 units lattice
create_box 2 simbox
create_atoms 1 box basis 1 1 basis 2 1 basis 3 1 &
basis 4 2 basis 5 2 basis 6 2 &
basis 7 2 basis 8 2 basis 9 2
mass 1 28.0855
mass 2 15.9994
group siliconatoms type 1
group oxygenatoms type 2
set group siliconatoms charge 2.4
set group oxygenatoms charge -1.2
Atoms interactions settings##################################
Si type 1, O type 2
#pair_style buck/coul/long 8 8
#pair_coeff 1 1 0.0 0.10 0.0
#pair_coeff 1 2 18003.7572 0.205205 133.5381
#pair_coeff 2 2 1388.7730 0.362319 175.0
pair_style table linear 10000
pair_coeff 1 1 BKSLJ.table SiSi
pair_coeff 1 2 BKSLJ.table SiO
pair_coeff 2 2 BKSLJ.table OO
kspace_style pppm 1.0e-4
neighbor 2.0 bin
neigh_modify every 1 delay 0 check yes
pair_write 1 2 1000 r 0.01 5.0 table.txt BKS_Si_O 2.4 -1.2
pair_write 2 2 1000 r 0.01 5.0 table.txt BKS_O_O -1.2 -1.2
pair_write 1 1 1000 r 0.01 5.0 table.txt BKS_Si_Si 2.4 2.4
Equilibrate temperature in NVT
fix 1 all nvt 300.0 300.0 100.0
velocity all create 450.0 5674845
timestep 0.00055
thermo_style custom step temp press &
ke pe etotal vol lx ly lz epair
thermo 1
dump 1 all atom 1000 dump1.qua
run 100000
NOW HERE IS AN EXAMPLE OF THE POTENTIAL TABLE FILE
table for BKS only Potential for LAMMPS
Si-O potential first, O-O potential second, SiSI third
4 columns with: index, distance, Potential, Force
SiO
N 10000 RSQ 0.0001 9.9991
1 0.0001 -1.33538E+26 -8.01229E+30
2 0.0011 -7.53788E+19 -4.11157E+23
3 0.0021 -1.557E+18 -4.44858E+21
4 0.0031 -1.50465E+17 -2.91222E+20
5 0.0041 -2.81127E+16 -4.11405E+19
6 0.0051 -7.58899E+15 -8.92823E+1
…
9997 9.9961 -4.148849365 -0.415113756
9998 9.9971 -4.148434293 -0.415030674
9999 9.9981 -4.148019304 -0.414947616
10000 9.9991 -4.147604398 -0.414864583
OO
N 10000 RSQ 0.0001 9.9991
1 0.0001 -1.75E+26 -1.05E+31
2 0.0011 -9.87829E+19 -5.38816E+23
3 0.0021 -2.04043E+18 -5.82981E+21
…
9998 9.9971 2.073974958 0.207369985
9999 9.9981 2.073767609 0.207328557
10000 9.9991 2.073560301 0.207287142
SiSi
N 10000 RSQ 0.0001 9.9991
1 0.0001 0 0
2 0.0011 0 0
3 0.0021 0 0
4 0.0031 0 0