The options for the van der Waals and electrostatic
energy terms are selected by an appropriate nbonds statement
(see Section 3.2.1).
Four combinations of nbonds options are possible.
The first is TRUNcation in combination with CDIE
,
which uses Lennard-Jones
and
Coulomb functions. The second involves a switched van der Waals
(VSWItch) and a
shifted electrostatic function (SHIFt) in combination with CDIE.
The third uses a switched van der Waals function (VSWItch) in
combination
with a switched electrostatic function (SWITch) and a 
dielectric
function (RDIE) . The fourth (REPEl > 0) uses the
so-called repel function , which is a
purely repulsive function without attractive or electrostatic
components. Any other combinations
of the SHIFt, SWITch, VSHIft, VSWItch, CDIE, RDIE, TRUNCation
and REPEl options are not possible and will produce an error message.
All nonbonded energy terms are truncated for atom pairs that are too close to each other (INHIbit option in the nonbonded statement, Section 3.2.1).
This feature reduces numerical instabilities in the case of strained initial coodinates or close contacts during high simulation temperatures.
