mapp.md.atoms.ff_lj

atoms.ff_lj(eps, sigma, r_c, shift=False, elems=None)

Lennard-Jones potential

see Notes section below

Parameters:

eps : symmetric double[nelems][nelems]

\epsilon

sigma : symmetric double[nelems][nelems]

\sigma

r_c : symmetric double[nelems][nelems]

r_c

shift : bool

shift the tail if set to True

elems : string[nelems]

mapping elements

Returns:

None

Notes

This is the famous Lennard Jones potential

U=\frac{1}{2}\sum_{i}\sum_{j\neq i}
\left\{\begin{array}{ll}
4\epsilon_{\alpha\beta}\biggl[\left( \frac{\sigma_{\alpha\beta}}{r_{ij}}\right)^{12}-\left( \frac{\sigma_{\alpha\beta}}{r_{ij}}\right)^6\biggr] &r_{ij}<r^{\alpha\beta}_c\\
0 &r_{ij}>r^{\alpha\beta}_c
\end{array}\right.

Examples

Kob-Anderson potential

>>> from mapp import md
>>> sim=md.cfg("configs/KA.cfg")
>>> sim.ff_lj(sigma=[[1.0],[0.8,0.88]],
              eps=[[1.0],[1.5,0.5]],
              r_c=[[2.5],[2.0,2.2]],
              shift=False,
              elems=['Ni','P'])