Multiwfn forum / Population Analysis (RESP charge fitting)

Re: Population Analysis (RESP charge fitting)

dummy@example.com (tsakash) — Fri, 07 Jun 2024 17:24:35 +0000

Thank you for your reply.

Re: Population Analysis (RESP charge fitting)

dummy@example.com (sobereva) — Fri, 07 Jun 2024 16:53:44 +0000

RESP is a good choice
However, if the polymer has a complicated structure with many branches, a much easier way is calculating EEM charge using Multiwfn (with the default EEM parameters trained for reproducing B3LYP/6-31G* CHELPG charges), which is quite fast and quality is usually acceptable.

Population Analysis (RESP charge fitting)

dummy@example.com (tsakash) — Fri, 07 Jun 2024 16:36:27 +0000

I have seen the suggestion of RESP(0.5) charges for MD simulation using nonpolarizable forcefield. If I want to run MD simulation for polymer melts, or polymer electrolytes where no other solvent is present, what is the suggested practice? I am using B3LYP/TZVP-MOLOPT with dftd3 in cp2k for geometry optimization and energy calculation. My polymer is a comb architecture polymer (a trimer) and I am restraining the middle unit to have zero charge so that I can transfer it to my md simulation.
Thank you.