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Study of the electronic structure of molecules. XV. Comments on the molecular orbital valency state and on the molecular orbital energies
Author(s) -
Clementi Enrico,
Routh Anne
Publication year - 1972
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.560060314
Subject(s) - valency , molecular orbital , ionization , atomic physics , ionization energy , ionic bonding , chemistry , electron , antibonding molecular orbital , non bonding orbital , molecule , ion , molecular orbital theory , ground state , double ionization , atom (system on chip) , homo/lumo , atomic orbital , physics , quantum mechanics , philosophy , linguistics , organic chemistry , computer science , embedded system
The valency state (vs) concept is analyzed in the Hartree–Fock approximation. A valency state “standard” is defined for atoms at infinite separation. A molecular orbital valency state (Movs) is defined from a partitioning technique (bond energy analysis) previously introduced for the Hartree–Fock molecular wave functions. The Movs for a given atom in a molecule is much higher in energy than the vs and its energy varies from molecule to molecule depending on the exact field of the surrounding atoms. The examples selected in the discussion are the CH 4 CH 3 F, CH 2 F 2 , CHF 3 and CF 4 molecules. An analysis of the orbital energies is then given in terms of the bond energy. The importance of the rearrangement effects following ionization of inner shell electrons (simulation of ESCA type experiments) is illustrated with computations of the positive ion for methane and its fluoroderivatives. It is concluded that rearrangement following ionization from inner shells is as important as rearrangements following ionization from valency electrons. A direct consequence is that the orbital energies should not be equated to the inner shell ionization potentials. The computation of such ionization potentials agrees to about 99.5% with ESCA data, when the energy of both the neutral and ionic species are computed; the use of the orbital energies limits this agreement to about 95%.