[gmx-users] By what tool is the atomptypes.atp file used?

[Elton Carvalho]

Dear gromacs users,

I'm developing a package to programmatically fit forcefield parameters for
new molecules and atom types, and it works by modifying .itp files (renamed
as .prm files in the CGenFF fashion) which are included by the .top files
to be tested against the ab-initio reference.

Studying the charmm forcefield directory (also OPLS), there's this
atomtypes.atp file that is referenced in old gromacs documentation[1] but
not in new docs [2].

My question is: where is this file used and is it essential in the
developing and testing phase of a new atomtype?

I understand the file's importance in documentation and I intend to update
it when releasing the modified forcefield, but I wonder whether adding a
new line in [atomtypes] with a name not present in atomptypes.atp will
result in problems (from obvious errors and warnings to more elusive,
2+2=5, ones).

Cheers form a sunny and warm (as usual) Natal,
Elton

References:
[1]
http://www.gromacs.org/Documentation/How-tos/Adding_a_Residue_to_a_Force_Field
[2]
http://manual.gromacs.org/documentation/current/user-guide/file-formats.html

-- 
Elton Carvalho