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EAM + electrostatic potential
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The EAM + electrostatic potential is a combination of the regular EAM model with an additional coulomb term.
$$ E_{tot}=E_{EAM} + \frac{1}{2} \sum_{i\neq j} E(r_{ij}) \quad \text{with} \quad E(r_{ij}) \sim \frac{q_{i}q_{j}}{r_{ij}} $$
Number of potential functions
To describe a system of $N$ atom types you need $N(N+2)$ potentials.
| # atom types | $\phi_{ij}$ | $f_{ij}$ | $g_i$ | Total # potentials |
|---|---|---|---|---|
| $N$ | $N(N+1)/2$ | $N(N+1)/2$ | $N$ | $N(N+2)$ |
| 1 | 1 | 1 | 1 | 3 |
| 2 | 3 | 3 | 2 | 8 |
| 3 | 6 | 6 | 3 | 15 |
| 4 | 10 | 10 | 4 | 24 |
Order of potential functions
The potential table is assumed to be symmetric, i.e. the potential for the atom types 1-0 is the same as the potential 0-1.
The order of the potentials in the potential file for $N$ atom types is:
$\phi_{00}, \ldots, \phi_{0N}, \phi_{11}, \ldots, \phi_{1N}, \ldots, \phi_{NN}$
$f_{00}, \ldots, f_{0N}, f_{11}, \ldots, f_{1N}, \ldots, f_{NN}$
$g_0, \ldots, g_N$