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Shaping the density to fit one‐electron properties: Constrained RHF calculations on N 2 , FH, CO, and LiH
Author(s) -
Zeiss G. D.,
Whitehead M. A.
Publication year - 1983
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.560240611
Subject(s) - wave function , basis set , parametrization (atmospheric modeling) , electron density , constraint (computer aided design) , eigenvalues and eigenvectors , function (biology) , basis (linear algebra) , property (philosophy) , chemistry , electron , computational chemistry , atomic physics , quantum mechanics , physics , statistical physics , density functional theory , mathematics , geometry , philosophy , epistemology , evolutionary biology , biology , radiative transfer
The molecular density required to give the correct values for one‐electron properties is rarely given by wave functions obtained from variation methods based on the total energy or the eigenvalues. Perhaps if we knew how the density should be shaped in any particular volume to fit a particular property, the whole molecular density might then be properly described to fit the whole volume. The secant‐parametrization procedure is used to constrain minimum basis set RHF wave functions for N 2 , FH, CO, and LiH to determine the effects of different constraints on RHF wave functions, and to see how constraints improve the quality of small basis set RHF wave functions. One‐electron property expectation values, energies, and unweighted and property weighted populations and electron density difference profiles are used to analyze the constrained wavefunctions. With the information from the constrained wave functions it should be possible to select a LCAO ‐ CI basis and states to give the correct density for all properties. This should map onto the constrained wave function in the region of the constraint and at the same time minimize the energy of the total molecular wave function. Such a density would be suitable for the density analyses favored by Bader and Nguyen‐Dang [Adv. Quantum Chem. 14 , 113 (1981)], Mezey [Theor. Chim. Acta 54 , 95 (1980); 58 , 309 (1981); 59 , 321 (1981)], and March [ Theoretical Chemistry (Royal Society of Chemistry, London, 1981), Vol. 4, p. 158], and show the real atom needed to generate the molecule.