AUXBASIS RI

[monika]

Hello,

I want to do optimization at MP2/6-31++G** level. I know that basis Dunning-like (aug-cc-pVDZ) is better, but I have to do calculation at Pople’s basis because of the time limit.
According to leads from TM Tutorial I’ve specified basis set library on my own. 
My question is, how can I specify basis set library in ri format ?

And the second question is, is it possible to prepare rimp2 calculation where ri is in aug-cc-pVDZ  basis and mp2 is in 6-31++G** basis ? [DSCF calculated at HF/6-31++G** level].

Best regards

M.

[Arnim]

Hi!

The auxiliary basis set library can be specified in the same way as for the orbital basis sets.
They are normally in $TURBODIR/cbasen.

In the CC2/MP2 menu is the topic cbas. There you can define any
auxiliary basis set that you like.
The orbital and auxiliary basis sets do not have to have the same name.
So your control file can look something like this:

$atoms
c  1                                                                     
   basis =c 6-31++G**
   cbas  =c aug-cc-pVDZ

But the auxiliary basis sets are not optimized for this. So you have to be careful.
In such case you have to analyse your RI error by comparing
RIMP2 calculations with conventional MP2.

Arnim

[christof.haettig]

Regarding the 6-31++G**: this is a strange choice for an MP2 geometry optimization... if you are limited by CPU time, and your system is an ordinary covalently bond molecule, I recommend to use TZVP instead. It will be more effecient and more accurate than 6-31++G**.

Christof