AMBER Archive (2008)

Subject: AMBER: Problem in calculation of resp charges using RED III

Date: Fri Aug 29 2008 - 01:56:24 CDT

Dear Amber users,

I want to calculate the resp charges and subsequently create a force field for
[fe3s4]+1. I was trying to do it in two ways:
1. Ab initio calculations in Gaussian 03 followed by the use of antechamber.
   The first few lines of my .com files are as follows:

#UB3LYP/gen pseudo=read SCF(maxcycle=1000) Test Pop=(MK,readradii) opt

Full optimization

1 2


2. Using REDIII-Tools- the input .com file was produced as follows:


#P hf/6-31G* Opt=(VTight,CalcFC) Freq SCF(Conver=8) Test

Optimization output to be used by R.E.D.

 1 2
 F 22.031 131.687 125.051
 F 19.837 133.121 124.065
 F 22.106 132.579 122.776
 S 19.888 131.269 124.910
 S 21.822 130.489 123.262
 S 21.887 133.677 124.533
 S 20.081 132.614 122.029

But in both the cases the following problem encountered was that the convergence
criterion is not met.
I dont know what else to do. I have already used variations like SCF=qc, but
nothing worked.
Urgent help is needed. Thanks a lot in advance.

Best Regards,
Moitrayee Bhattacharyya
Molecular Biophysics Unit,
Indian Institute of Science.
Bangalore-560 012

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