Firefly and PC GAMESS-related discussion club

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sanya
sanya@photonics.ru

Indeed, d type functions in all basis sets are given as XX, YY, etc. cartesian components. With d5 on, the program constructs a correct x^2-y^2 function and removes the contaminant s-orbital. And indeed, some basis sets were optimized with cartesian functions and, therefore, turning d5 on with them may result in the energies of atoms (or whatever was used for basis optimization) that are not so good as with d5 off. On the contrary, for basis sets optimized with spherical functions, turning d5 off will impair the benchmark results. However, my experience says that turning d5 on is usually OK for any basis set (and ensures consistency with, say, Gaussian calculations). Anyway, we are mostly interested not only in atoms and diatomics...

On Wed Jan 20 '10 1:00pm, Roman Zubatyuk wrote
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>1. FF does not ignore this option. I can not agree with Sanya ;)
>2. Basically, if you use spherical d-type basis function, you get correct set 5 orbitals (xy, yz, xz, z^2, x^2-y^2). In the case of cartesian representation, you will get 6 orbitals (xy, yz, xz, x^2, y^2, z^2), 5 of which will be d-type orbitals, plus one contaminant s-orbital. Similar for f-functions.
>So, the choice between use of cartesian and spherical basis functions should be made based on the knowledge either contaminant s-orbital was regarded when the basis set was constructed, or not.
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>On Wed Jan 20 '10 11:39am, Vyacheslav wrote
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>>On Wed Jan 20 '10 0:23am, Roman Zubatyuk wrote
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>>OK, Roman. Then some more questions:
>>1) If Firefly ignores the d5 option for spherical basis sets (as Sanya speaks about it), then how the program finds out that this basis set is spherical? Personally I do not allow Firefly to read any articles.

>>2) Childlike question: what for the d5 option is necessary? It is not necessary for spherical basis sets, and for cartesian ones it is better no to use this option, since it misrepresents results - it was already discussed at this forum earlier and also I have own sad experience of this option' use for Cartesian basis set. Probably I do not understand something...
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>>> Some bases are were parametrized with cartesian d and higher functions, some with spherical. So, in general, you need to look at the original paper presenting the basis set. Most of the modern basis sets were parametrized using spherical harmonics. Pople's 6-31G basis sets were parametrized with cartesian d-functions, but 6-311G were not.

>>>Regards,
>>> Roman.
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