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Re^4: FIREFLY based comments on speeds and accuracies of SBKJC vs 6-31G? (SOLVED)

Siddheshwar Chopra

Dear Alex,
Thank you for the information.


On Mon May 5 '14 3:04am, Alex Granovsky wrote
>Dear Siddheshwar,

>for a fixed atomic basis set, CPU requirements of large SCF jobs
>scales approximately as the square of the overall number of atoms.

>For the fixed number and types atoms, CPU requirements of large
>SCF jobs scales approximately as the fourth power of the overall
>number of basis functions.

>The latter means that SBKJC should be faster but not dramatically
>faster as it removes only a small fraction of AOs.  

>Kind regards,
>Alex Granovsky
>On Sat Apr 19 '14 6:32pm, Siddheshwar Chopra wrote
>>Dear Alex,
>>Thats an important information. Thanks again. Alex could you comment on their speeds? Logically if they reduce the no. of basis functions, then they should be really fast. I want to be sure about their speeds before using them. It would be good if you could compare their speeds with the 6-31G and its variants.


>>On Fri Apr 18 '14 9:10pm, Alex Granovsky wrote
>>>Dear Siddheshwar,

>>>for second row elements ECPs are computationally inefficient as
>>>they remove only single orbital (i.e. 1s) per atom. If you use
>>>SBK, you still need to add polarization function(s) to get
>>>reasonable results. SBK basis for Li, Be, B, C, N, O, and F
>>>atoms has only two L-type (i.e. combined S and P) shells for
>>>valence electrons and thus it is (approximately) a DZV-quality
>>>basis set.

>>>Kind regards,
>>>Alex Granovsky
>>>On Tue Apr 15 '14 1:24pm, Siddheshwar Chopra wrote
>>>>Dear All,
>>>>This is the first time I am using SBKJC ECPs for the same samples for which I used 6-31G basis sets. Could anyone point out their speed and accuracy comparisons (Firefly based)? As per Jensen's book I read that for the second row elements, SBKJC gives almost same error as that of TZP. And I have never used TZPs. I have till now worked with only 6-31G and variants.


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