This type specifies the Lennard-Jones potential with
periodic boundary conditions (minimum image convention.[53]
The box lengths in the , and
directions and the cutoff (as a fraction of the smallest box length)
must be specified using the *PARAMS* keyword in the `odata` file.
Setting a negative value for the cutoff fraction means that all minimum
images are included.
Subroutines used: **ljpdiff**.
If the *BINARY* keyword is specified then a binary Lennard-Jones
potential is used[55] along with subroutine **ljpbin** or **ljpshift**.

David Wales
2017-09-21