[AMBER] Query about QM/MM calculation using Amber/Gaussian interface

From: Kshatresh Dutta Dubey <kshatresh.gmail.com>
Date: Fri, 13 Jun 2014 12:16:03 +0300

Dear Users

    I am using Amber 14 for QM/MM calculation with Gaussian as external
interface. I have to optimize a system containing some amino acids and a
ligand in QM regions. I found that Amber automatically adds some keywords
in route section of Gaussian input that force Gaussian to do single point
calculations. For example, I used :
* mem = '2GB'*
*! method = 'B3LYP',*
*! basis = '6-31G',*
* use_template =1,*
* num_threads = 2*
* /*
for &gau namelist and :

*#P OPT B3LYP/6-31G SCF=(Conver=8)*

for template file namelist. The calculations runs fine and it shows normal
termination, but I found that it does only single point calculation not
optimizing the structure while I have mentioned optimization in route
sections. I notice that Amber adds some additional keyword such as 'Force'
in route section which restricts Gaussian to calculate forces only. I guess
it is fine for QM-MM/MD since we need forces for dynamics, but here I am
interested in QM/MM optimization only. The route section modified by Amber
is :

*#P OPT B3LYP/6-31G SCF=(Conver=8) NoSymm Force Guess=Read Charge Prop=*
* (Field,Read)*

How can I disable 'Force' keyword so that I can perform proper
optimization. I will be thankful for your help.

With best regards
Dr. Kshatresh Dutta Dubey
Post Doctoral Researcher,
c/o Prof Sason Shaik,
Hebrew University of Jerusalem, Israel
Jerusalem, Israel
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Received on Fri Jun 13 2014 - 02:30:02 PDT
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