[lammps-users] Forces in REAXFF and AIREBO Different ?

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1

Hi ,

I am doing the same calculation using airebo and reaxff potentials for an 8 atom graphene box. But the forces which I get by displacing the first atom in x y and z direction via set command are not quite the same. Could you please throw some light on this.

data file for reaxff: -

8 atoms
1 atom types

0 4.841712 xlo xhi
0 4.19304558980796200928 ylo yhi
-50 50 zlo zhi
-2.420856 0 0 xy xz yz

Masses

1 12.0110

Atoms

1 1 0 0.000000000000 0.000000000000 0.000000000000
2 1 0 2.420856000000 0.000000000000 0.000000000000
3 1 0 -1.210428000000 2.096522794904 0.000000000000
4 1 0 1.210428000000 2.096522794904 0.000000000000
5 1 0 1.210428000012 0.698840931628 0.000000000000
6 1 0 3.631284000012 0.698840931628 0.000000000000
7 1 0 0.000000000012 2.795363726532 0.000000000000
8 1 0 2.420856000012 2.795363726532 0.000000000000

Forces ( both in eV/Angstom) :-

AIREBO
-0.356081628547 -0.004628302382 -0.033918829587
0.022267797657 0.000365004314 0.001712654756
0.007945609914 -0.008588438652 0.001698548406
0.008516621525 0.007828804483 0.001727561038
0.148868311906 0.073877807728 0.011145064286
0.145299350967 -0.069823020879 0.012074259921
-0.000004734573 -0.000000063768 -0.006067923946
0.023188671151 0.000968209156 0.011628665126

REAXFF
0.032844094973 -0.004066946788 -0.012887389317
-0.239379781197 -0.002356043774 -0.015264140084
0.011756447428 0.147744575948 -0.015208144925
0.011851481461 -0.142277002904 -0.015317945222
0.091580721877 0.000129812419 0.017633923011
0.084282529581 0.000291119195 0.016634480728
-0.081015809558 0.001468994316 0.007263794792
0.088080315434 -0.000934508412 0.017145421018

  • Regards
    lammps_user
2

Why do you expect them to be the same for 2 different potentials?

Steve

3

It seems you are asking a AIRBE vs ReaxFF question, not a LAMMPS
question. Assuming the implementation of the 2 potentials is correct (and
there could be bugs, but no known ones at this point).

Steve