User defined parameter file for molecular dynamics


Click here for full thread
Just Got Here
As I understand it in order to use a user defined parameter file a correctly formatted file with the extension .par has to be in the same directory as the calculation that I'm running. I've looked at the supplied parameter files but I am unclear about some things.

1. Where do I define the electrical charge for atoms?

2. How do I define bonds as being rigid (like in TIP4P water) or constrained (like in SPC/E water)?

3. Is it possible to use different forms of van der Waals interaction other than Lennard-Jones 12-6 (i.e. Morse or Buckingham potentials), and if so how?

Any help would be greatly appreciated.