# Trouble in G94 with MP2 Freq (Summary)

*From*: "Pablo Vitoria" <qibvigap |-at-|
lg.ehu.es>
*Subject*: Trouble in G94 with MP2 Freq (Summary)
*Date*: Mon, 26 Apr 1999 11:57:36 +0200

Hi all,
Thanks to Customer Service of Gaussian (Doug Fox) and Stefan Fau for their
replies to my question. In brief, G94 does not support analytic second
derivatives for ECP basis sets, although G98 does.
The answers and original question follow.
Pablo
------------------
(From Cust. Service Doug)
Dr. Garcia,
G94 does not support analytic second derivatives for ECP basis sets.
We have added that in G98 but you can use FREQ with MP2 in G94 and to these
with finite differences by specifying FREQ or FREQ=HPModes. In general
MP2 by itself with memory and MAXDisk specified will make good choices on
other MP2 options.
-------------------
(From Stefan Fau)
Dear Pablo,
>from the name of your chk-file and your choice of basis set I assume
that your molecule contains Pt. If this is true, you have a problem.
Pt should be treated with an ECP to include linear relativistic effects,
but G94 is not able to calculate analytic 2nd derivatives if ECPs are
present. This feature is implemented in G98 only.
Stefan
-------------------
(Original Question)
This is the first time I tried to calculate the IR spectrum with MP2, and
I have the following problem. I read in the manual that analytical
frequencies need MP2=SEMIDIRECT. So I used the following input:
%Mem=14MW
%Chk=/temporal/qipguloj/ptcno4.chk
#P MP2=(SEMIDIRECT,VERYSTINGY)/LANL2DZ GUESS=READ MAXDISK=1100MB FREQ=
(ANALYTIC,HPMODES) GEOM=CHECKPOINT
(rest omitted)
And the computation stopped with:
Analytic MP2 frequencies require a (semi-)direct transformation.
Error termination via Lnk1e in /usr/local/g94/l1.exe.
Job cpu time: 0 days 0 hours 0 minutes 0.4 seconds.
I would appreciate any help. Could it be that analytical frequencies are
not available with core potentials (LANL2DZ is an only-valence basis set,
with core replaced by an ECP).
Thank you very much
Pablo
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Pablo Vitoria Garcia
Dpto. Quimica Inorganica, Facultad de Ciencias
Universidad del Pais Vasco (UPV/EHU)
Aptdo. 644
E-48080 Spain
Phone: +34 94 6012000 Ext. 5529
Fax: +34 94 4648500
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