Si Erhart Albe tersoff potential


I refer to the Si_Erhart Albe.tersoff file in LAMMPS folder potentials.
After comparing the formulae in the LAMMPS documentation with that of the
paper, I think the beta in the LAMMPS formula is different from that of the
paper. The confusion arises because in the tersoff file, there are some
comments which define lambda1, lambda 2 etc from line 7 onwards which seem
to refer to beta of the paper while the comment m=n=beta=1 seems to refer to
the beta of LAMMPS. Here, I would like to ask whether these two beta's (beta
in definition of lambda1 and beta in m=n=beta) are indeed different and
which one refers to what.

Thank you,

Like all potential files that we release with LAMMPS, we are fairly
confident in the validity of SiC_Erhart-Albe.tersoff. We also put a
fair amount of effort in to the documentation, which is non-trivial,
given that different authors use different notation, etc. In all of
this, we aim primarily for internal consistency, so that the code does
what we say it does, no more, no less. We can not attempt to fully
document every notation used by every group and map it on to LAMMPS
notation. In some cases, we provide some hints in the form of
comments in the potential file e.g.

# lambda1=beta*sqrt(2*S)

This is saying that LAMMPS lambda1 equals the formula on the right,
which presumably uses Albe's notation, including Albe's beta.
However, the beta in the file is still the LAMMPS beta, not Albe's

I hope this helps you.