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Reliability of atomic natural orbital basis sets in calculations involving pseudopotentials
Author(s) -
Sousa C.,
Rubio J.,
Illas F.
Publication year - 1992
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.540130205
Subject(s) - basis set , sto ng basis sets , atomic physics , diatomic molecule , atom (system on chip) , valence (chemistry) , basis (linear algebra) , chemistry , molecular orbital , computational chemistry , density functional theory , mathematics , physics , quantum mechanics , molecule , linear combination of atomic orbitals , geometry , computer science , embedded system
The performance of Atomic Natural Orbital (ANO) basis sets for calculations involving nonempirical core pseudopotentials has been studied by comparing the results for atomic and molecular nitrogen obtained using contracted ANO basis sets with those obtained using both the primitive set and a segmented one. The primitive set has been optimized at the SCF level for atomic N treated as a five‐electron pseudo‐atom, and consists of 7 s and 7 p primitive GTOs supplemented by 2 d and 1 f GTOs optimized at the CI level. From this primitive set three contracted [3 s 3 p 2 d 1 f ] sets have been obtained. The first one has been derived from the ANOs of the neutral atom, the second has been obtained from an averaged density matrix and the third one is a segmented set. For the atom, the segmented set gives a zero contraction error at the SCF level as it must be in valence‐only calculations. The ANO basis sets show some small contraction error at the SCF level but perform better in CI calculations. However, for the diatomic N 2 molecule the ANO basis sets exhibit a rather large contraction error in the calculated SCF energy. A detailed analysis of the origin of this error is reported, which shows that the conventional strategy used to derive ANO basis sets does not work very well when pseudopotentials are involved.