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Pair‐excitation MCSCF treatment of small molecules in an optimized Slater–Transform–Preuss basis set
Author(s) -
Guner O. F.,
Shillady D. D.,
Ottenbrite R. M.,
Rao B. K.,
Yurtsever E.
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.560320502
Subject(s) - basis set , basis (linear algebra) , chemistry , excitation , atomic orbital , basis function , sto ng basis sets , wave function , atomic physics , computational chemistry , quantum mechanics , physics , mathematics , linear combination of atomic orbitals , geometry , electron , density functional theory
Pair‐excitation multiconfigurational self‐consistent field ( PEMCSCF ) treatment of 11 small molecules (LiH, BeH 2 , BH 3 , BF, CH 4 , C 2 H 4 , C 2 H 2 , CH 2 O, NH 3 , H 2 O, and HF) has been carried out in a minimum basis set of Slater Transform Preuss functions as fitted by six cartesian gaussians ( STP ‐6G). The advantages of accuracy without using a split basis are shown by comparison to familiar 4‐31G and 6‐31G calculations using molecular geometries optimized with STO ‐6G basis sets. A benefit is shown for the use of minimum basis fitted to STP functions: they overemphasize long‐tail radial dependence to achieve long range basis sensitivity without increasing the basis size at the AO ‐to‐ MO transformation step in the configuration interaction portion of the MCSCF algorithm. Fully optimized STP ‐6G parameters are given and appear to be transferable as shown for acrolein. A FORTRAN listing of the full least squares fitting algorithm is available* for in situ generation of STP ‐6G orbitals energetically superior to 4‐31G, or a less accurate STP ‐6G 1S, 2S, and 2P basis may be scaled directly as if they were STO ‐6G functions, but with considerably lower energy that with an STO ‐6G basis.