born potential

[111151]

Hi：

I will use the pair_style born which has the following form in LAMMPS manual, the last two terms have opposite mathematics operators, “-” and “+” respectively, and in the examples of this manual, C and D has the same sign.

When I do my calculations in LAMMPS, if I set the D as negative numbers,

pair_coeff 1 1 0.2640625 0.317 2.340 1.05 -0.5
pair_coeff 1 2 0.21125 0.317 2.755 7 -8.6875
pair_coeff 2 2 0.1584375 0.317 3.170 72.5 -145.625

the calculation comes up with " nan";
and if I set the D as positive numbers, the calculation can go down.

pair_coeff 1 1 0.2640625 0.317 2.340 1.05 0.5
pair_coeff 1 2 0.21125 0.317 2.755 7 8.6875
pair_coeff 2 2 0.1584375 0.317 3.170 72.5 145.625

Well, in some other references, the last two terms have the same mathematics operator, and also do the corresponding C, D coefficients, as follows

So, I wonder that maybe there is something wrong in the manual file.
I would appreciate your help!
Thank you very much!

Jia Wang

[Carlos_Campana]

The manual seems consistent with the code. See pair_born.cpp for example. The C coefficient identified as
born2[][] appears with a minus sign up front while D, born3[][[] with a plus one.

You have to make sure that your system is configured as its supposed to be as a change in sign may result in huge forces acting on the atoms. Make sure as well you are employing the right units, etc. Run always a simple test before proceeding ahead with your production runs.

Carlos