Subject: Re: Re: CCL:CPCM TS location

From: "zjwu" <[email-masked]>
Date: Thu, 24 Apr 2003 13:13:16 +0800

Dear Dr. Hess,

I mean the job failing because the structure is not the TS structure anymore. The calculation may converge but goes to different geometry which I did not want. I have tried to read force constants at cpcm calculation from either gas phase frequency calculation or Onsager frequency calculation (these frequencies are obtained based on the optimized geometry) (calculation using Onsager model works well for the TS calculation). In addition, I also tried opt=(ts,calcfc), but as you know, calcfc does not exist for cpcm. It seems g03 is possible to calculate fc at cpcm level.

Hope I have made myself clear.

Thank you very much for your answer.

Best regards,

Zhijian Wu

Dear Dr. Zhijian Wu,
    Is this job failing because it runs out of optimization cycles? I'd 
need to know more details about what is going wrong before I make 
detailed suggestions, but one possible way to improve this calculation 
is to calculate the force constants in the solution phase, then use 
these force constants to start the transition state search. Usually the 
gas-phase Hessian is a good enough approximation, but in some cases 
where the gas-phase and solution-phase potential energy surfaces are 
different enough, explicitly calculating the second derivatives in the 
solution phase can be helpful. Incidentally, if you are using G98, the 
CPCM second derivatives will be performed by numerical differentiation 
of the analytic gradients and if you are using G03, the second 
derivatives will be calculated analytically.

Regards,
Jim Hess

++++++++++++++++++++++++++
James Hess, Ph.D.
Customer Support Scientist
Gaussian, Inc.
e-mail: [email-masked]
++++++++++++++++++++++++++

On Tuesday, April 22, 2003, at 08:29 PM, zjwu wrote:

>>  Dear members,
>> 
>>  ?/DIV> 
>> 
>>  I am trying to locate the transition state using cpcm model. The 
>>  initial structure is from gas phase optimized transition structure 
>>  (with correct vibrational mode). The optimization at cpcm level fails 
>>  by the following keywords
>> 
>>  ?/DIV> 
>> 
>>  #b3lyp/6-31g(d,p) opt=(ts, readfc, noeigen) scrf=(cpcm,solvent=water)
>> 
>>  ?/DIV> 
>> 
>>  Do anybody has experience in cpcm transition structure calculation?
>> 
>>  ?/DIV> 
>> 
>>  Thanks a lot.
>> 
>>  ?/DIV> 
>> 
>>  Best regards,
>> 
>>  ?/DIV> 
>> 
>>  Zhijian Wu
>> 
Dear Dr. Zhijian Wu,

   Is this job failing because it runs out of optimization cycles? I'd
need to know more details about what is going wrong before I make
detailed suggestions, but one possible way to improve this calculation
is to calculate the force constants in the solution phase, then use
these force constants to start the transition state search. Usually
the gas-phase Hessian is a good enough approximation, but in some
cases where the gas-phase and solution-phase potential energy surfaces
are different enough, explicitly calculating the second derivatives in
the solution phase can be helpful. Incidentally, if you are using G98,
the CPCM second derivatives will be performed by numerical
differentiation of the analytic gradients and if you are using G03,
the second derivatives will be calculated analytically.

Regards,

Jim Hess

++++++++++++++++++++++++++

James Hess, Ph.D.          

Customer Support Scientist

Gaussian, Inc.

e-mail: [email-masked]

++++++++++++++++++++++++++

On Tuesday, April 22, 2003, at 08:29 PM, zjwu wrote:

<< excerpt> Dear members,

?/DIV> 

I am trying to locate the transition state using cpcm model. The
initial structure is from gas phase optimized transition structure
(with correct vibrational mode). The optimization at cpcm level fails
by the following keywords

?/DIV> 

#b3lyp/6-31g(d,p) opt=(ts, readfc, noeigen) scrf=(cpcm,solvent=water)

?/DIV> 

Do anybody has experience in cpcm transition structure calculation?

?/DIV> 

Thanks a lot.

?/DIV> 

Best regards,

?/DIV> 

Zhijian Wu

<< /excerpt>