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I understand that there are many different methods that can be used to approximate the set of MOs for an arbitrary molecule, as the actual quantum mechanical description is taxing to calculate. I just wanted to know which computational method comes closest to reality. B3LYP/6-31G(d) seems to be a popular choice, but I realize that there many others such as RHF/STO-3G, MP2/MINI, etc.

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  • $\begingroup$ If there were one single method that would come closest to reality, who would bother to use (or remember, for that matter) the rest of them? $\endgroup$ – Ivan Neretin Jul 25 '16 at 18:03
  • $\begingroup$ @IvanNeretin, those people without access to the computer time they need. Inferior methods are constantly used to avoid using years of CPU time for trivial things, no? $\endgroup$ – NotEvans. Jul 25 '16 at 18:06
  • $\begingroup$ Full CI would be about the most exact thing you can do as it is only limited by the basis set employed. But it is too time consuming to be used for most practical problems. $\endgroup$ – Philipp Jul 25 '16 at 18:10
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    $\begingroup$ I'm voting to close this - it's incredibly broad and opinion-based (e.g., what exact property you mean). Different methods are good for different properties. Consider, e.g., chemistry.stackexchange.com/questions/27302/… $\endgroup$ – Geoff Hutchison Jul 25 '16 at 18:11