different SIA formation energy for same input script

_hossain_khan_via_Go · July 27, 2020, 7:04pm

Dear Sir

I want to measure the interstitial (SIA) formation energy for core-shell Ti_TiO2. But I am getting different SIA formation energy for the same input script when I ran these two simulations in two different computers (One in my computer and another in cluster computer). In one computer I am getting SIA formation energy 0.166691317223012 and in another computer, I am getting -38.0848504657624

Can you tell me the reason? and what should I do for getting correct SIA formation energy?

One output
LAMMPS (7 Aug 2019)
OMP_NUM_THREADS environment is not set. Defaulting to 1 thread. (src/comm.cpp:93)
using 1 OpenMP thread(s) per MPI task
units metal # set ‘metal’ units (Angstrom,ps timescale)
dimension 3
boundary p p p # periodic BCs
atom_style charge
neighbor 2.0 bin
neigh_modify every 1 delay 0 check yes

----------------------- ATOM DEFINITION ----------------------------

read_data core_tight.lmp
orthogonal box = (0 0 0) to (151.5 151.5 151.5)
2 by 2 by 4 MPI processor grid
reading atoms …
148314 atoms
read_data CPU = 0.272803 secs
write_dump all atom all_atom.lammpstrj
WARNING: Calling write_dump before a full system init. (src/write_dump.cpp:80)

mass 1 47.86700000
group type1 type 1
70466 atoms in group type1
mass 2 15.99900000
group type2 type 2
77848 atoms in group type2

------------------Define Interatomic Potential -----------------

pair_style comb3 polar_off
pair_coeff * * ffield.TiO.comb3 Ti O #Ti
Reading potential file ffield.TiO.comb3 with DATE: 2014-02-01

compute eng all pe/atom
compute eatoms all reduce sum c_eng

#----------------------Run Minimization-------------------------
reset_timestep 0

thermo 10
thermo_style custom step pe lx ly lz press pxx pyy pzz c_eatoms

dump 1 all custom 400 before.dump id type xs ys zs c_eng

min_style cg
minimize 1e-15 1e-15 5000 5000
Neighbor list info …
update every 1 steps, delay 0 steps, check yes
max neighbors/atom: 2000, page size: 100000
master list distance cutoff = 13
ghost atom cutoff = 13
binsize = 6.5, bins = 24 24 24
1 neighbor lists, perpetual/occasional/extra = 1 0 0
(1) pair comb3, perpetual
attributes: full, newton on, ghost
pair build: full/bin/ghost
stencil: full/ghost/bin/3d
bin: standard
Per MPI rank memory allocation (min/avg/max) = 58.4 | 76.46 | 94.65 Mbytes
Step PotEng Lx Ly Lz Press Pxx Pyy Pzz c_eatoms
0 -851611.25 151.5 151.5 151.5 -17596.904 -24169.772 -24294.841 -4326.0988 -851611.25
10 -870122.97 151.5 151.5 151.5 -18930.084 -23199.883 -23273.779 -10316.592 -870122.97
20 -875696.54 151.5 151.5 151.5 -11381.48 -15075.386 -15143.418 -3925.6354 -875696.54
30 -876798.07 151.5 151.5 151.5 -9934.0069 -13588.059 -13664.5 -2549.4616 -876798.07
40 -877619.2 151.5 151.5 151.5 -9182.1671 -12817.215 -12879.841 -1849.4458 -877619.2
50 -878347.52 151.5 151.5 151.5 -8351.5157 -11886.06 -11961.664 -1206.8234 -878347.52
60 -878921.24 151.5 151.5 151.5 -7729.5754 -11175.077 -11243.359 -770.29016 -878921.24
70 -879326.29 151.5 151.5 151.5 -7116.0431 -10492.679 -10573.561 -281.88968 -879326.29
80 -879606.47 151.5 151.5 151.5 -6564.404 -9883.6843 -9967.3445 157.81678 -879606.47
90 -879852.78 151.5 151.5 151.5 -6014.3257 -9258.6147 -9312.3787 528.01627 -879852.78
100 -880044.13 151.5 151.5 151.5 -5605.5733 -8772.1155 -8845.5878 800.98335 -880044.13
110 -880238.63 151.5 151.5 151.5 -5149.9948 -8227.5708 -8330.4056 1107.992 -880238.63
120 -880357.1 151.5 151.5 151.5 -4842.6554 -7848.682 -7946.3441 1267.0598 -880357.1
130 -880448.31 151.5 151.5 151.5 -4605.8061 -7528.4969 -7664.5144 1375.5931 -880448.31
140 -880529.33 151.5 151.5 151.5 -4279.7875 -7100.5812 -7238.3883 1499.6069 -880529.33
150 -880602.45 151.5 151.5 151.5 -4066.2469 -6805.5109 -6952.9699 1559.7402 -880602.45
160 -880662.55 151.5 151.5 151.5 -3902.5435 -6565.5283 -6715.0471 1572.9448 -880662.55
170 -880707.57 151.5 151.5 151.5 -3751.0369 -6348.9526 -6494.1097 1589.9516 -880707.57
180 -880751.73 151.5 151.5 151.5 -3559.7997 -6046.5026 -6183.6522 1550.7557 -880751.73
190 -880798.67 151.5 151.5 151.5 -3382.1887 -5766.8745 -5889.9877 1510.296 -880798.67
200 -880822.84 151.5 151.5 151.5 -3278.1633 -5617.5046 -5730.3427 1513.3575 -880822.84
210 -880841.55 151.5 151.5 151.5 -3183.7531 -5478.4759 -5597.7176 1524.9342 -880841.55
220 -880859.33 151.5 151.5 151.5 -3041.0869 -5253.4551 -5393.2102 1523.4045 -880859.33
230 -880878.99 151.5 151.5 151.5 -2949.4446 -5112.6258 -5259.844 1524.136 -880878.99
240 -880891.09 151.5 151.5 151.5 -2839.6177 -4932.6357 -5068.2544 1482.037 -880891.09
250 -880907.7 151.5 151.5 151.5 -2718.1495 -4739.2937 -4865.5924 1450.4377 -880907.7
260 -880927.05 151.5 151.5 151.5 -2635.2562 -4639.6374 -4757.3758 1491.2445 -880927.05
270 -880946.12 151.5 151.5 151.5 -2548.9632 -4531.4663 -4639.2066 1523.7834 -880946.12
280 -880962.66 151.5 151.5 151.5 -2430.3529 -4384.1934 -4481.0117 1574.1463 -880962.66
290 -880980.53 151.5 151.5 151.5 -2326.9661 -4255.6884 -4355.6878 1630.4779 -880980.53
300 -880994.36 151.5 151.5 151.5 -2214.9497 -4099.5591 -4194.4406 1649.1504 -880994.36
310 -881004.11 151.5 151.5 151.5 -2112.1552 -3955.1838 -4059.3787 1678.0969 -881004.11
320 -881018.17 151.5 151.5 151.5 -2054.8087 -3876.8471 -3981.115 1693.5359 -881018.17
330 -881024.71 151.5 151.5 151.5 -1996.4579 -3806.0334 -3899.0192 1715.6789 -881024.71
340 -881035.16 151.5 151.5 151.5 -1953.2685 -3743.5333 -3843.231 1726.9586 -881035.16
350 -881041.87 151.5 151.5 151.5 -1900.0901 -3671.3843 -3761.2431 1732.357 -881041.87
360 -881047.94 151.5 151.5 151.5 -1819.6112 -3566.5782 -3647.0829 1754.8275 -881047.94
370 -881052.85 151.5 151.5 151.5 -1714.9611 -3424.572 -3508.9575 1788.6463 -881052.85
380 -881062.01 151.5 151.5 151.5 -1616.1504 -3304.7435 -3369.0873 1825.3795 -881062.01
390 -881067.07 151.5 151.5 151.5 -1573.3653 -3241.4648 -3320.119 1841.4879 -881067.07
400 -881075.36 151.5 151.5 151.5 -1499.8476 -3145.2234 -3230.2004 1875.8809 -881075.36
410 -881079.18 151.5 151.5 151.5 -1458.0896 -3092.2411 -3175.1867 1893.1591 -881079.18
420 -881082.34 151.5 151.5 151.5 -1399.4622 -3015.4883 -3098.3792 1915.4809 -881082.34
430 -881091.52 151.5 151.5 151.5 -1354.4278 -2961.5141 -3039.2015 1937.4322 -881091.52
440 -881096.54 151.5 151.5 151.5 -1318.9186 -2912.1489 -2991.9015 1947.2946 -881096.54
450 -881100.11 151.5 151.5 151.5 -1277.8382 -2854.0145 -2937.3459 1957.8457 -881100.11
460 -881102.31 151.5 151.5 151.5 -1224.8446 -2781.8176 -2871.0449 1978.3287 -881102.31
470 -881106.37 151.5 151.5 151.5 -1126.8945 -2654.8126 -2743.5018 2017.6308 -881106.37
480 -881111.07 151.5 151.5 151.5 -1063.4616 -2575.2085 -2661.9108 2046.7345 -881111.07
490 -881120.22 151.5 151.5 151.5 -1040.8587 -2541.6148 -2630.5498 2049.5883 -881120.22
500 -881123.54 151.5 151.5 151.5 -1014.1931 -2506.9983 -2597.6761 2062.0951 -881123.54
510 -881124.87 151.5 151.5 151.5 -974.5219 -2454.073 -2543.644 2074.1513 -881124.87
520 -881127.53 151.5 151.5 151.5 -915.09551 -2380.4932 -2463.7248 2098.9316 -881127.53
530 -881130.86 151.5 151.5 151.5 -876.5794 -2331.4266 -2409.9642 2111.6526 -881130.86
540 -881133.51 151.5 151.5 151.5 -843.39472 -2288.4767 -2366.3503 2124.6428 -881133.51
550 -881134.88 151.5 151.5 151.5 -808.12517 -2244.2755 -2324.5957 2144.4957 -881134.88
560 -881135.49 151.5 151.5 151.5 -792.5137 -2226.1867 -2304.8317 2153.4773 -881135.49
570 -881137.08 151.5 151.5 151.5 -761.28245 -2189.7404 -2265.4288 2171.3219 -881137.08
580 -881138.7 151.5 151.5 151.5 -723.5416 -2144.0757 -2222.179 2195.6299 -881138.7
590 -881142.19 151.5 151.5 151.5 -679.4321 -2089.3545 -2166.1829 2217.2411 -881142.19
600 -881143.35 151.5 151.5 151.5 -667.76368 -2074.0504 -2152.5004 2223.2597 -881143.35
610 -881143.5 151.5 151.5 151.5 -655.1597 -2058.6739 -2138.7357 2231.9305 -881143.5
620 -881144.42 151.5 151.5 151.5 -596.38241 -1986.8146 -2070.474 2268.1414 -881144.42
630 -881145.34 151.5 151.5 151.5 -581.56717 -1970.3237 -2052.7873 2278.4096 -881145.34
640 -881145.66 151.5 151.5 151.5 -570.37083 -1955.8774 -2037.4921 2282.257 -881145.66
646 -881145.73 151.5 151.5 151.5 -564.91349 -1949.9275 -2031.7575 2286.9445 -881145.73
Loop time of 2602.99 on 16 procs for 646 steps with 148314 atoms

100.0% CPU use with 16 MPI tasks x 1 OpenMP threads

Minimization stats:
Stopping criterion = linesearch alpha is zero
Energy initial, next-to-last, final =
-851611.254874 -881145.730559 -881145.730559
Force two-norm initial, final = 12235.1 2.02604
Force max component initial, final = 1811.34 0.590998
Final line search alpha, max atom move = 2.98252e-09 1.76266e-09
Iterations, force evaluations = 646 1108

akohlmey · July 28, 2020, 3:19am

you are running with a different number of MPI ranks, and have two
different versions of LAMMPS, possibly compiled with different
compilers or different settings.
all of these differences can result in small numerical differences in
forces due to floating-point math properties. since you also plenty of
atoms in your system it is quite possible, that the minimization of
the two systems will "find" different local(!) minima due to the high
dimensionality of the problem in combination with the numerical noise.

you can clearly see the increasing divergence of the minimizations in
the energies when comparing the outputs.

if you then add an atom at the same location to two different
geometries, you will see a difference in total energies and energy
differences.

it actually would be very unusual, if those two runs would result in
the exact same result. you would have to have a smooth and not very
rugged potential hypersurface for that or perfect symmetry which would
reduce the number of degrees of freedom or both, so that even with
small differences in the initial forces, the system would always
converge to the same (local) minimum. having a minimization algorithm
find the global minimum is a known "hard" problem for high-dimensional
systems.

axel.

_hossain_khan_via_Go · July 28, 2020, 3:41pm

Dear Sir

thank you for your quick response. this answer will help me a lot.