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Molecular calculations with the MODPOT , VRDDO , and MODPOT / VRDDO procedures. IV. Boron hydrides and carboranes
Author(s) -
Popkie Herbert E.,
Kaufman Joyce J.
Publication year - 1977
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.560120514
Subject(s) - chemistry , ab initio , boron , molecule , valence (chemistry) , diatomic molecule , ab initio quantum chemistry methods , dipole , molecular orbital , crystallography , computational chemistry , analytical chemistry (journal) , atomic physics , physics , organic chemistry
Reference completely ab initio 6–3G and nonempirical 3G/ MODPOT ( ab initio effective core model potential) LCAO ‐ MO ‐ SCF calculations (using the same valence atomic orbital basis) were performed for a series of boron hydrides (B 4 H 10 , B 5 H 9 , B 5 H 11 , and B 6 H 10 ) and a test 3G/ MODPOT + VRDDO (variable retention of diatomic differential overlap for charge conserving integral prescreening) calculation were also performed for B 5 H 9 , B 6 H 10 , and B 10 H 14 . The agreement between the ab initio 6–3G and the corresponding 3G/ MODPOT calculations was excellent for valence orbital energies, gross atomic populations, and dipole moments. The results also compared favorably to previous ab initio minimum STO basis results of Lipscomb and coworkers. The 3G/ MODPOT + VRDDO calculations verified that for such spatially compact molecules (such as boron hydrides, which are fragments of polyhedra), the VRDDO procedure does not result in a noticeable savings in computer time for molecules of the size and shape of B 5 H 9 and B 6 H 10 , in contrast to the savings previously realized for organic molecules of comparable atomic size. However, the agreement in calculational results between the 3G/ MODPOT and the 3G/ MODPOT + VRDDO results was still as extremely close as it had been for the organic molecules. 3G/ MODPOT calculations were also carried out for B 8 H 12 , B 9 H 15 , B 10 H 14 , B 10 H 14 −2 , 1,2‐C 2 B 4 H 6 , and 1,6‐C 2 B 4 H 6 and the results compared to the previous minimum STO basis results. For B 10 H 14 , the 3G/ MODPOT + VRDDO method led to savings in computer time of 28% over the 3G/ MODPOT method itself. The agreement of the 3G/ MODPOT results with available experimental photoelectron spectral data for B 5 H 9 and 1,6‐C 2 B 4 H 6 was as good as that of the previous ab initio minimum STO basis calculations.