I am using # opt freq=(raman,vcd) b3lyp/lanl2dz pop=(nbo,savenbo) scf=qc geom=connectivity for geometry optimization+other calculations of an organic molecule. I am getting the results using this function in a day or two. However, if I use 6-311+G(d,p), the same calculation runs for months and can still not achieve the results. Can please anyone answer whether I can stay with the outcome using lanl2dz, or should I go for 6-311....
Thank you
Dear Tejaswi Ashok Hegde,
Could you share your research molecules (formula or name)? Regarding to LANL2DZ, it is so small basis set, you should merely use it to guess the initial geometry structures. In your case, the minimum basis set level should be 6-31g(d,p) or 6-31+g*. Please share to you a attached file of basis set, beside that you can refer more at the following links:
1) https://www.basissetexchange.org/
2) https://gaussian.com/basissets/
Best regards.
Hi, Tejaswi Ashok Hegde.
To best of my knowledge, LANL2DZ basis set is used for molecules that contains heavy metal atoms/transition metals. Even in papers, LANL2DZ is mentioned only if the compounds involved contain metals. Since I do not know what your molecule looks like, I would like to suggest a website where you can choose basis sets based on the elements present in your molecule. https://www.basissetexchange.org
Perhaps you could use lower basis sets first since 6-311+G(d,p) took months to complete its calculation.
Hope this helps.
Dear Dang T. Nguyen and Nur Aqilah Zahirah Norazmi,
Thanks for your time and answers. It is beneficial.
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