Pseudo Jahn—Teller origin of square-planar configuration instability of main-group-element hydrides

The vibronic origin of the instability of the square-planar configuration of the [AH 4] p hydrides of the second- and third-row elements (A = B, C, N, O, Al, Si, P and S) is revealed by means of ab initio MO—LCAO—RHF calculations of the electronic wavefunctions, vibronic contants and bare force cons...

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Bibliographic Details
Published in:Journal of molecular structure 1992-07, Vol.270, p.369-380
Main Authors: Bersuker, I.B., Gorinchoi, N.N., Polinger, V.Z.
Format: Article
Language:English
Subjects:
Atomic and molecular physics
Exact sciences and technology
Molecular properties and interactions with photons
Molecular spectra
Physics
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Summary:The vibronic origin of the instability of the square-planar configuration of the [AH 4] p hydrides of the second- and third-row elements (A = B, C, N, O, Al, Si, P and S) is revealed by means of ab initio MO—LCAO—RHF calculations of the electronic wavefunctions, vibronic contants and bare force constants using the STO-4G** basis set. The vibronic pseudo Jahn—Teller effect is confirmed as the only cause of instability. It is shown that the main contribution to the instability is due to the vibronic mixing of the ground A 1g state with two excited B 2u states formed by one-electron excitation a 2u → b * 1g (or b 1g → a * 2u) and e u → e * g (in the frozen MO approximation for the excited states). The variation of the vibronic parameters and instability in the above series is discussed.
ISSN:0022-2860
1872-8014
DOI:10.1016/0022-2860(92)85040-N