Lennard-Jones potential

The Lennard-Jones potential has the following functional form

\[E = \sum_{ij} V(r_{ij})\]

where

\[V(r) = 4 \varepsilon \left[ \left(\frac{\sigma}{r}\right)^{12} - \left(\frac{\sigma}{r}\right)^{6} \right].\]

Here, \(\varepsilon\) and \(\sigma\) are the two potential parameters that, respectively, define energy and length scale. The potential is truncated beyond a certain cutoff.

The following code snippet, to be inserted in the <potentials> block of the input file illustrates the definition of this potential type in the input file.

<lennard-jones id="Lennard-Jones" species-a="*" species-b="*">
  <sigma>2.5</sigma>
  <epsilon>0.5</epsilon>
  <cutoff>10.0</cutoff>
  <fit-dof>
    <sigma />
    <epsilon />
  </fit-dof>
</lennard-jones>

Elements and attributes

• <sigma>: The initial value for the \(\sigma\) parameter.

• <epsilon>: The initial value for the \(\varepsilon\) parameter.

• <cutoff>: The cutoff radius.