# 2 potentials for the same atomic species: possible ?

Dear mailing list,

Is it possible to let LAMMPS use two different potentials for the same atomic species ?

I explain better.

Suppose we have a potential that is the sum of two potentials of known shape, with no common parameter between them:
P(tot) = P1 + P2.

Let us suppose that P1 and P2 are implemented already in LAMMPS
(example:P1 = Tersoff; P2 = electrostatic interactions or lennard-jones or whatever).

I would like to have

-) the total energy of the atoms = E(P1) + E(P2)

-) the total forces acting on the atoms = F(due to P1) + F(due to P2)

In my case:

P1 = reference-free meam (that I am implementing)
P2 = electrostatic interaction with variable charges (that I will implement soon)

So I need to know this in order to think the programming strategy accordingly.

In particular:

1. is this possible now ? Or should I implement it (since I need it) ?

2. if possible what is the syntax of the input file to make it happen ?

3. if possible should I take care of a particular way to implement the potentials to let this happen ?

Thank you very much in advance

Bests,

Daniele Scopece

Dear mailing list,

Is it possible to let LAMMPS use two different potentials for the same
atomic species ?

I explain better.

Suppose we have a potential that is the sum of two potentials of known
shape, with no common parameter between them:
P(tot) = P1 + P2.
Let us suppose that P1 and P2 are implemented already in LAMMPS
(example:P1 = Tersoff; P2 = electrostatic interactions or lennard-jones or
whatever).

I would like to have
-) the total energy of the atoms = E(P1) + E(P2)
-) the total forces acting on the atoms = F(due to P1) + F(due to P2)

In my case:
P1 = reference-free meam (that I am implementing)
P2 = electrostatic interaction with variable charges (that I will implement
soon)
So I need to know this in order to think the programming strategy
accordingly.

In particular:
1) is this possible now ? Or should I implement it (since I need it) ?

it is possible now. in much more flexible ways even. you can use the
hybrid/overlay pair style for it.

2) if possible what is the syntax of the input file to make it happen ?

see the manual.

3) if possible should I take care of a particular way to implement the
potentials to let this happen ?

no. just follow the implementation of similar potentials.

axel.