Hi everyone
I am currently performing a npt simulation on a minimized structure of tobermorite . My simulation cell consist of 3888 atoms and I am using three pair styles: buck, sw and coul/long. I am not sure how to use the ewald summation command (kspace style) in Lammps. I am not clear on the selction of a “precision value”. In lammps, it says that This value is used in conjunction with the pairwise cutoff to determine the number of K-space vectors for style ewald. I used a precision value of 0.0001, works well for energy minimization, however when I applied NPT conditions (300k, 0bars), the system aborts at 100 fs. I also tried using a precision value of 10 and got a really large pressure after energy minimization, however I can perform NPT without system aborting. I am not sure why this is happening. Can someone assist me with this problem.
Sample Output file
boundary p p p
atom_style charge
pair_style hybrid/overlay buck 3.0 sw coul/long 3.0
kspace_style ewald 10.0
read_data data7.hamid
orthogonal box = (0 0 0) to (34.48 22.17 68.33)
2 by 1 by 4 processor grid
3888 atoms
pair_coeff 1 1 buck 4369.01 0.29 0.0
pair_coeff 1 8 buck 4369.01 0.29 0.0
pair_coeff 2 2 buck 1171.52 0.29 0.0
pair_coeff 6 7 buck 248.6324 0.29 0.0
pair_coeff 3 7 buck 248.6324 0.29 0.0
pair_coeff * * coul/long
pair_coeff * * sw SiOOO.sw NULL Si O NULL NULL NULL NULL NULL
neighbor 2.0 bin
neigh_modify delay 5
equilibrate
min_style cg
thermo 5
minimize 1.0e-4 1.0e-6 120 1000
Ewald initialization …
G vector = 0.334871
vectors: actual 1d max = 0 -2147483648 -2147483648
Memory usage per processor = 3.51844e+13 Mbytes
Step Temp E_pair E_mol TotEng Press
0 0 -126519.67 0 -126519.67 -247601
4 0 -128950.76 0 -128950.76 -349464.88
Minimization stats:
Stopping criterion = energy tolerance
Energy initial, next-to-last, final =
-126519.672709 -128947.109705 -128950.761085
Force two-norm initial, final = 463.721 283.049
Force max component initial, final = 18.2084 8.58276
Final line search alpha, max atom move = 4.52249e-05 0.000388154
Iterations, force evaluations = 4 21
Pair time (%) = 0.0220845 (79.4304)
Kspce time (%) = 0.000148773 (0.535087)
Neigh time (%) = 0 (0)
Comm time (%) = 0.00470981 (16.9396)
Outpt time (%) = 0 (0)
Other time (%) = 0.000860482 (3.09487)
Nlocal: 486 ave 510 max 462 min
Histogram: 2 1 1 0 0 0 0 1 1 2
Nghost: 1376.38 ave 1451 max 1298 min
Histogram: 2 0 0 0 2 1 1 0 0 2
Neighs: 10329.8 ave 10662 max 9969 min
Histogram: 2 2 0 0 0 0 0 0 0 4
FullNghs: 20659.5 ave 21597 max 19707 min
Histogram: 2 2 0 0 0 0 0 0 1 3
Total # of neighbors = 165276
Ave neighs/atom = 42.5093
Neighbor list builds = 0
Dangerous builds = 0
300-NPT
velocity all create 300.0 5812775
fix 1 all npt 300.0 300.0 0.001 xyz 0.0 0.0 1.0 drag 1.0
fix 1 all npt 300 300 0.001 aniso 0.0 0.0 0.0 0.0 0.0 0.0 0.04 drag 1.0
thermo 200
thermo_style custom step temp etotal press
thermo_modify flush yes
timestep 0.0001
run 5000000
Ewald initialization …
G vector = 0.334871
vectors: actual 1d max = 0 -2147483648 -2147483648
Memory usage per processor = 3.51844e+13 Mbytes