Hello,
I’m using Tersoff potential for SiO interactions and I want to compute “pair/local” and “property/local” data.
As written in the documentation, the single() fonction is missing : what does it mean ? Is there any workaround to compute those data with Tersoff, SW or homemade potentials?
Thank you in advance,
Alexandre
alexandre,
Hello,
I'm using Tersoff potential for SiO interactions and I want to compute
"pair/local" and "property/local" data.As written in the documentation, the single() fonction is missing : what
does it mean ? Is there any workaround to compute those data with Tersoff,
SW or homemade potentials?
there is no workaround. the underlying assumption of the
Pair::single() method is that pairwise forces and energies
are pairwise additive.
thus there _cannot_ be a meaningful implemention
for many-body potentials. in lammps those potentials
are implemented as pairwise potentials (with a twist).
if you write your own custom pair style, then you are free
to implement the Pair::single() method. lammps will work
without, except for some small subset that requires this
to work, like the computes you mention or the option to
dump a collective pairwise interaction to a table.
cheers,
axel.
If all you want to calculate with compute pair/local
is the distances then the error check could be
removed. Ditto for compute property/local. But
if you want energy or forces, then what Axel
said is correct. Tersoff does not support computing
pairwise energy/force b/c it's a manybody potential,
and it makes no sense to ask it to do it.
Steve