[gmx-users] New force fields

[Erik Lindahl]

Hi,

We should have AMBER, CHARMM& OPLS working relatively soon, but since 
we're anyway moving to the new XML formats in the next version it might 
be smart to think if there are additional strange parameter formats or 
forcefields with strange interactions, so we can prepare the force field 
descriptions for this.

There are a couple of things I've thought about, but I'd be happy for 
more suggestions. We should try to add support for:

1. Separate bonded and nonbonded atom types. This is already done - it's 
quite useful for OPLS with 965 different nonbonded atom types.
 (965^4=8.7e11 dihedral definitions is a little unnecessary...)

2. Proper & improper dihedral definitions that use either 4 or 2 atoms. 
Wildcards should also be ok in all interactions. This is essentially 
finished too.

3. Automated generation of 1-3 (Urey-Bradley) interactions. These can be 
defined as pairs now, but it should be cleaner & automatic.

Are there other features used by some force fields? Some ancient 
versions of AMBER used to need 10-12 interactions, but I don't think 
anybody is using it now...

Cheers,

Erik