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- Peter Pulay
- Department of Chemistry, University of Arkansas, Fayetteville, Arkansas 72701
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- Tracy P. Hamilton
- Department of Chemistry, University of Arkansas, Fayetteville, Arkansas 72701
抄録
<jats:p>A simple way of generating starting orbitals for multiconfigurational SCF calculations (particularly of the CAS type) is to use the natural orbitals of the unrestricted Hartree–Fock wave function. Significant fractional occupancy of a UHF natural orbital indicates that the orbital should be included in the active space; this is illustrated for symmetrically stretched water, for NO, N2O4, and for the transition state on the Me3CO→Me2CO+CH3 reaction surface. Average natural orbitals should be used if there are several UHF solutions for the same state; this restores symmetry broken at the the UHF level. Configuration selection based on fractional occupation appears to be the basis for a reliable automated procedure. The UHF natural orbitals provide good starting orbitals for the two-configuration SCF and for the 4×4 CAS wave function in stretched F2, H2O2, and C2H6, methane, water, in twisted ethylene, in ozone, and for various CAS wave functions in the first asynchronous transition state of the HCNO+H2C2 1,3-cycloaddition. Comparison is made with the extended Hartree–Fock method.</jats:p>
収録刊行物
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- The Journal of Chemical Physics
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The Journal of Chemical Physics 88 (8), 4926-4933, 1988-04-15
AIP Publishing
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詳細情報 詳細情報について
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- CRID
- 1360292619933329280
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- NII論文ID
- 30015658922
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- DOI
- 10.1063/1.454704
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- ISSN
- 10897690
- 00219606
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- データソース種別
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