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The 3‐21G(N*) basis set: An economical polarized basis set for ab initio studies on nitrogen‐containing molecules
Author(s) -
Riggs Noel V.,
Radom Leo
Publication year - 1987
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560310310
Subject(s) - basis set , basis (linear algebra) , nitrogen , chemistry , ab initio , computational chemistry , set (abstract data type) , molecule , nitrogen inversion , inversion (geology) , atomic physics , molecular physics , mathematics , physics , geometry , computer science , density functional theory , organic chemistry , programming language , paleontology , structural basin , biology
The 3‐21G basis set shares with its older cousin, the 4‐31G basis set, a tendency to overestimate valence angles at nitrogen atoms and to underestimate seriously barriers to inversion at such atoms. The 6‐31G* basis set generally yields greatly improved results in these respects. It is here shown that, for a variety of molecules, supplementation of the 3‐21G basis set at three‐ or two‐coordinate nitrogen atoms with a set of six d ‐functions having exponent 1.0 leads to optimized geometries and inversion barriers at such nitrogen centers in good agreement with results obtained with the 6‐31G* basis set. This supplemented basis set, designated as 3‐21G(N*), also leads to calculated vibrational frequencies in good agreement with those calculated with the 6‐31G* basis set. The 3‐21G(N*) basis set offers an economical alternative to the 6‐31G* basis set, particularly for molecules containing several first‐row atoms other than nitrogen.