From: DENILSON FERREIRA DE OLIVEIRA (denilson_at_dqi.ufla.br)
Date: Sun Apr 29 2012 - 06:37:04 CDT

Dear Chris,

As I told you before, I am trying to develop parameter and topology files for a dianion using Force Field Toolkit (FFTK). Consequently, I would appreciate if you could help me with:

1) In “Opt.Charges” -> “Advanced Settings” -> “Optimize settings”, there are two “modes”: “downhill” or “simulated annealing”. Any suggestion/advice ?

2) For the optimization of bond and valence angle force constants a scaling factor of 0.89 must be applied to the MP2/6-31G* force constant matrix. Is this scaling included in the calculation carried out in the “Cal. Bonded” window of FFTK ?

3) In the “Water Int.” window FFTK generates three compound-water Gaussian input files for the oxygen of each carbonyl group. Am I supposed to use the three corresponding log files (output of Gaussian calculation) in the “Water Interaction Energy Data” of the “Opt. Charges” window ?

4) In the “Opt Charges” -> “Water interaction Energy Data”, one of the parameters is “weight”. Is there any rule for choosing the appropriate value for this parameter ?

Thank you very much for your attention.

Best regards.

Denilson.

Denilson F. Oliveira
Laboratório de Produtos Naturais
Departamento de Química
Universidade Federal de Lavras