Dear lammps users,
According to the lammps-manual the parameters n, beta, lambda2, B, lambda1 and A for pair_style tersoff are only used for two-body interactions and can therefore be set to zero in entries of the potential-file where the 2nd and 3rd element are different. If one looks at the equations however, setting the parameters n and beta to zero effectively means excluding all three-body interactions, since the parameter zeta is then no longer relevant, since it will be multiplied by zero.
Simply replacing the zeros for n and beta in a tersoff potential file by ones however, does not change anything in the results. (I've tried different potential files with different materials). this seems to imply that there is something wrong in the implementation in lammps of the tersoff pair style.
Am I correct or am I missing something?
Kind regards,
Astrid
Dear lammps users,
According to the lammps-manual the parameters n, beta, lambda2, B, lambda1
and A for pair_style tersoff are only used for two-body interactions and
can therefore be set to zero in entries of the potential-file where the 2nd
and 3rd element are different. If one looks at the equations however,
setting the parameters n and beta to zero effectively means excluding all
three-body interactions, since the parameter zeta is then no longer
relevant, since it will be multiplied by zero.
Simply replacing the zeros for n and beta in a tersoff potential file by
ones however, does not change anything in the results. (I've tried
different potential files with different materials). this seems to imply
that there is something wrong in the implementation in lammps of the
tersoff pair style.
Am I correct or am I missing something?
that is not quite how it works. if you have a 3-body term, the
corresponding 2-body parameters are redundant, i.e. the Si-C pairwise
parameters have to be the same for Si-C-Si and Si-C-C. what the
documentation means to express is that one of them, Si-C-C, is used and the
other one ignored.
as far as i can tell your experiments confirm this. if you have evidence to
the contrary, please provide it.
axel.