From: Francesco Pietra (
Date: Thu Aug 20 2015 - 10:13:52 CDT


I posted recently about ffTK OPT MP2 problems, no answer, however it became
clear that the shared memory on a node (120GB) was not enough, and could
not be increased. On the other hand, Gaussian is threaded, so that I can't
exploit the enormous resources of the cluster.

Therefore, my question is, is OPT at MP2 really needed for getting a good
ff for ligands along ffTK in the realm of classical MD? OPT at SCF level,
followed by single-point MP2 is not enough? I understand that it depends on
what one is looking for, from simple docking to normal mode calculations,
so that my question covers all situations.

If SCF followed by single-point MP2 is not enough, the only alternative
that I can see is to break the ligand into pieces and carry out OPT/MP2 on
each piece, allowing for the approximations in reforming the whole ligand.

Thanks a lot for advice on strategy.

francesco pietra