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Re^3: Relativistic and non-relativistic basis sets.

Thomas Pijper

Dear Pavlo,

ANO-RCC is much, much larger than cc-pVDZ, so I would say that a mixed ANO-RCC / cc-pVDZ set is very unbalanced. I personally would distrust any results obtained this way.

Though I do not know what you want to calculate, I would generally recommend to use a pseudopotential if you would like to consider relativistic effects somewhat. The cc-pVXZ-PP sets by Peterson are available for copper and can be used in combination with the normal cc-pVXZ sets for lighter elements.

Kind regards,

On Wed Feb 5 '14 8:46pm, Pavlo Solntsev wrote
>Dear Thomas.

>Basically, i have two basis sets: GC ANO-RCC and cc-pVDZ. The heaviest element is copper. I don't expect high relativistic effects from copper. I would like to use the contracted ANO-RCC for Cu and the contracted cc-pVDZ for all other elements. I was wondering about possibility to mix these basis sets. This is not a technical issue, but more methodological.
>Thanks for any comments.

>On Wed Feb 5 '14 1:50pm, Thomas Pijper wrote
>>Dear Pavlo,

>>Technically, there is no problem in combining two basis sets in one input file. However, I do not see why you would use a relativistic basis set in Firefly as it is not capable of relativistic calculations such as Douglas–Kroll–Hess or Dyall's Modified Dirac. Also, I would be cautious when mixing basis sets of considerably different qualities (such as using an unpolarized DZ set with a heavily polarized TZ set).

>>Could you perhaps explain your question a bit more?
>>Kind regards,
>>On Mon Feb 3 '14 9:01pm, Pavlo Solntsev wrote
>>>Dear Alex.

>>>I was asked about possibility to use relativistic and non-relativistic basis sets in FF. I mean, is it ok if we combine two different basis sets in one input file?


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