Subject: summary-scaling vibrational frequencies

From: "sanja" <[email-masked]>
Date: Fri, 9 Jun 1995 09:27:13 -0700

Hi,

Here is the summary of the responses answering my question about scaling
calculated vibrational frequencies. Original question was:

>   I am interested in scaling vibration frequencies calculated at the
>MP2/6-31G** level. Should I use the scaling factor of 0.9427, proposed by
>J.A. Pople et.al for the MP2/6-31G* calculated frequencies. I am not sure
>how much this scaling factor is sensitive to the difference in the basis sets.
>Every comment is wellcome.
>
>  Thanx,
>      Sanja

and the answers ...

***************************************************************************
Hello, this is a reply to your posting on the CCL about scaling factors.
I believe it is most important to consider what molecule, cluster, or other
system of particles you are calculating. If there is an experimental ir
available, this should be used to develope your own set of scaling factors.
These results can be compared with "standard" published scaling factors. This
is not a very difficult task.
One reason to support the calculation of one's own set of scaling factors is
that different scaling factors are sometimes needed even within a range of
stretching frequencies (free OH, as opposed to H-bonded OH stretches) as well
as a set for bending frequencies. (Burke, Krishnan, and Jensen, Chem Ph Let.,
vol206,p293(1993); vol217,p311(1994), as only one example (water clusters)).
There are quite a few discussions in the literature about this subject, and I
expect you will get many more replies to your question.

Luke Anthony Burke              tel:609-225-6158
Department of Chemistry	        fax:609-225-6506
Rutgers University              e-mail:
Camden, NJ 08102                [email-masked]
USA

***************************************************************************
Since HF frequencies are only approximate, I'd recommend a less precise
scaling factor.  O.9 is good for HF/6-31G* or HF/DZP frequencies.

Dave Ewing
John Carroll University
[email-masked]

There is some data that DFT frequencies might not need much scaling.  DFT
might be much faster than MP2 for this....The DFT method of choice is ?

Regards,

John

--

John M. McKelvey			email: [email-masked]
Computational Science Laboratory	phone: (716) 477-3335
2nd Floor, Bldg 83, RL
Eastman Kodak Company
Rochester, NY 14650-2216

--

***************************************************************************
Dear Sanja,

Probably the best way to obtain a scaling factor, which is certainly better
than a generic scaling factor for a particular level of theory, is to
perform another ab initio calculation at the same level of theory on an
analogous molecule for which the vibrational frequencies are known.  One
can then apply the scaling factor which best suits the known molecule to
the molecule in question.

Yours sincerely,

Ryan
*************************************
* Dr Ryan P.A. Bettens,             *
* Department of Physics,            *
* 174 West 18th Ave.,               *
* Columbus, OH 43210-1106,          *
* U.S.A.                            *
*                                   *
* email: [email-masked] *
* Phone: (614) 292 4492             *
*************************************

***************************************************************************
The original poster asked about scaling factors to be applied to mp2/6-31g**
calculated frequencies. He asked if our mp2/6-31g* scaling factor is
applicable and if the scalinf factor varies with basis set.

Our work in this area, which is nearing completion, indicates that the mp2
level of theory is not particularly sensitive to basis set in predicting
frequencies. While the 6-31g** basis set was not studied, we have data for the
6-311g** basis set. The appropriate scaling factor for the mp2 level of theory
with this basis set is 0.9496 (with about the same overall RMS error as wefound
for the mp2/6-31g* level of theory).

We have actually studied a very extensive range of methods (including DFT) with
various basis sets. If readers would like further information then please
contact me.
Hi,

Here is the summary of the responses answering my question about scaling
calculated vibrational frequencies. Original question was:

>   I am interested in scaling vibration frequencies calculated at the
>MP2/6-31G** level. Should I use the scaling factor of 0.9427, proposed by
>J.A. Pople et.al for the MP2/6-31G* calculated frequencies. I am not sure
>how much this scaling factor is sensitive to the difference in the basis sets.
>Every comment is wellcome.
>
>  Thanx,
>      Sanja

and the answers ...

***************************************************************************
Hello, this is a reply to your posting on the CCL about scaling factors.
I believe it is most important to consider what molecule, cluster, or other
system of particles you are calculating. If there is an experimental ir
available, this should be used to develope your own set of scaling factors.
These results can be compared with "standard" published scaling factors. This
is not a very difficult task.
One reason to support the calculation of one's own set of scaling factors is
that different scaling factors are sometimes needed even within a range of
stretching frequencies (free OH, as opposed to H-bonded OH stretches) as well
as a set for bending frequencies. (Burke, Krishnan, and Jensen, Chem Ph Let.,
vol206,p293(1993); vol217,p311(1994), as only one example (water clusters)).
There are quite a few discussions in the literature about this subject, and I
expect you will get many more replies to your question.

Luke Anthony Burke              tel:609-225-6158
Department of Chemistry	        fax:609-225-6506
Rutgers University              e-mail:
Camden, NJ 08102                [email-masked]
USA

***************************************************************************
Since HF frequencies are only approximate, I'd recommend a less precise
scaling factor.  O.9 is good for HF/6-31G* or HF/DZP frequencies.

Dave Ewing
John Carroll University
[email-masked]

There is some data that DFT frequencies might not need much scaling.  DFT
might be much faster than MP2 for this....The DFT method of choice is ?

Regards,

John

--

John M. McKelvey			email: [email-masked]
Computational Science Laboratory	phone: (716) 477-3335
2nd Floor, Bldg 83, RL
Eastman Kodak Company
Rochester, NY 14650-2216

--

***************************************************************************
Dear Sanja,

Probably the best way to obtain a scaling factor, which is certainly better
than a generic scaling factor for a particular level of theory, is to
perform another ab initio calculation at the same level of theory on an
analogous molecule for which the vibrational frequencies are known.  One
can then apply the scaling factor which best suits the known molecule to
the molecule in question.

Yours sincerely,

Ryan
*************************************
* Dr Ryan P.A. Bettens,             *
* Department of Physics,            *
* 174 West 18th Ave.,               *
* Columbus, OH 43210-1106,          *
* U.S.A.                            *
*                                   *
* email: [email-masked] *
* Phone: (614) 292 4492             *
*************************************

***************************************************************************
The original poster asked about scaling factors to be applied to mp2/6-31g**
calculated frequencies. He asked if our mp2/6-31g* scaling factor is
applicable and if the scalinf factor varies with basis set.

Our work in this area, which is nearing completion, indicates that the mp2
level of theory is not particularly sensitive to basis set in predicting
frequencies. While the 6-31g** basis set was not studied, we have data for the
6-311g** basis set. The appropriate scaling factor for the mp2 level of theory
with this basis set is 0.9496 (with about the same overall RMS error as wefound
for the mp2/6-31g* level of theory).

We have actually studied a very extensive range of methods (including DFT) with
various basis sets. If readers would like further information then please
contact me.

Hope this is of some assistance,

Kind Regards,

Anthony P. Scott
Research Officer
Computational Chemistry Group
Research School of Chemistry
Australian National University
Canberra, ACT, Australia

   Thanx to you all who replyed to my question.

   Sanja

Hope this is of some assistance,

Kind Regards,

Anthony P. Scott
Research Officer
Computational Chemistry Group
Research School of Chemistry
Australian National University
Canberra, ACT, Australia

   Thanx to you all who replyed to my question.

   Sanja

-- 
*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
Sanja Sekusak                         e-mail: [email-masked]
Rudjer Boskovic Institute             phone: (385-1) 46 10 89
HR-41001 Zagreb, CROATIA              fax: (385-1) 27 26 48           
*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*