vdwcutoff or cutoff.
The main option that effects van der Waals interactions
is the switching parameter. With this option set to on,
a smooth switching function will be used to truncate the
van der Waals potential energy smoothly at the cutoff distance.
A graph of the van der Waals
potential with this switching function is shown in Figure
1. If switching is set to off, the
van der Waals energy is just abruptly truncated at the cutoff
distance, so that energy may not be conserved.
See section 5.1.4 for more details.
The switching function used is based on the X-PLOR switching
function. The parameter switchdist specifies the distance
at which the switching function should start taking effect to
bring the van der Waals potential to 0 smoothly at the cutoff distance.
Thus, the value of switchdist must always be less than that
of cutoff.
