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

Берсукер, И. Б.; Gorinchoi, N.N.; Polinger, V. Z.

doi:10.1016/0022-2860(92)85040-n

Cited by 20 publications

(23 citation statements)

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“…As an example of a more complicated crystal structure, high-To copper oxides were considered. The calculated atomic charges for La2CuO 4 (Table 3) are close to those obtained by fitting phonon spectra within the point charge model and those obtained by direct quantum chemistry calculations [10,11]. As one could expect from the beginning, this compound was found to be more ionic than Y-BaCu superconductors (Table 4).…”

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confidence: 58%

On the simple determination of the self-consistent atomic charges and Madelung potentials in ionic crystals

Chibotaru

Gorinchoi

Solonenko

et al. 1997

Chemical Physics Letters

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A simple method for the self-consistent calculation of the atomic charges and Madelung potentials in ionic crystals is suggested. The method is based on electronegativity equalization and permits the obtaining of good charge distributions. Test calculations are carried out for a number of structures like cubic perovskites, high-T c copper oxides and mixed valence crystals. © 1997 Published by Elsevier Science B.V.Electrostatic or Madelung potentials are important characteristics of ionic and near ionic crystals, determining their electronic structure and physical properties. Numerous calculations of the electronic structure of crystals and molecular fragments of crystals have shown that the Madelung potentials must be included in the calculation schemes to obtain the correct energy level ordering, adequate values of the atomic charges and energy gaps [1][2][3][4]. Evaluation of the Madelung potentials implies knowledge of the atomic charges which in their turn can be obtained as the result of complicated quantum chemistry calculations. In this connection the elaboration of simple quantitative methods seems worthwhile. In this Letter a procedure for the self-consistent calculation of atomic charges and Madelung potentials in ionic crystals based on the electronegativity equalization method (EEM) [5] is suggested. It permits the obtaining of good charge distributions and is further simplified for ionic crystals of cubic symmetry.The electronic energy of an ionic crystal is supposed to be a function of atomic charges qk only and is presented in the form N

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confidence: 58%

On the simple determination of the self-consistent atomic charges and Madelung potentials in ionic crystals

Chibotaru

Gorinchoi

Solonenko

et al. 1997

Chemical Physics Letters

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“…Note that the vibronic constants It was proved analytically and confi rmed by a series of numerical calculations [4][5][6][7] that for any molecular system…”

Section: Methods and Computational Detailsmentioning

confidence: 99%

“…in [1][2][3]). It has also been shown that the only reason of instability of the high-symmetry nuclear confi gurations and structural distortions of any molecular system in the non-degenerate state is the pseudo Jahn-Teller effect (PJTE), that is the vibronic mixing of considered state with the appropriate by symmetry excited states [1,2,[4][5][6][7]. Hence the instabilities should be sought for in the electronic states which mix strongly under nuclear displacements, and vice versa.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…If there is instability, there should be corresponding excited states that cause the instability of the reference confi guration. The electronic control of the instabilities via vibronic coupling has been considered in detail in a series of papers [4][5][6][7][8][9][10][11][12][13].One of the examples of electronic control on nuclear confi guration instability is the stabilization of vertically excited states. The available experimental and theoretical data indicate that in the electronically excited states molecules may adopt equilibrium geometries very different from those in the ground states.…”

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Electronic Control of Molecular Configuration Instability via Vibronic Coupling. Pseudo Jahn-Teller Stabilization of Vertically Excited States of F2CO, N2H2 and H2C2O Molecules

Gorinchoy¹

2014

ChemJMold

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Abstract. The pseudo Jahn-Teller effect is employed to explain the origin of distortions of carbonyl fl uoride, diazene and ketene molecules in the lowest singlet and triplet excited states. The ground state and the excited electronic states of considered molecules were calculated by ab initio SCF CI method with the use of the 631G-type basis set. The corresponding pseudo Jahn-Teller coupling constants are estimated by fi tting the ab initio data for the adiabatic potential curves of the molecules to the general formula, obtained from the vibronic theory. With these data an explanation of both the larger instability of the triplet excited states as compared with the singlet ones and the elongation of the corresponding bond distances in the excited states is obtained.Keywords: Pseudo Jahn-Teller effect, stereochemistry, excited states, carbonyl fl uoride, diazene, ketene. IntroductionThe stereochemistry of molecular systems is determined by their electronic structure and the permutation symmetry of identical atoms. The latter means that from the viewpoint of symmetry any molecule must possess the spatial structure with the highest possible symmetry. However, depending on the electronic state the high-symmetry nuclear confi guration can become unstable, and the molecule is distorted. Any perturbation of molecular system (excitation, ionization, coordination to transition metal complexes etc.) changes its electronic state and, as a consequence, may lead to distortion of its nuclear confi guration.The problem of electronic control on nuclear confi guration instability has already some history. In the case of degenerate electronic states the confi guration instability is a direct consequence of the Jahn-Teller effect (See, e.g. in [1][2][3]). It has also been shown that the only reason of instability of the high-symmetry nuclear confi gurations and structural distortions of any molecular system in the non-degenerate state is the pseudo Jahn-Teller effect (PJTE), that is the vibronic mixing of considered state with the appropriate by symmetry excited states [1,2,[4][5][6][7]. Hence the instabilities should be sought for in the electronic states which mix strongly under nuclear displacements, and vice versa. If there is instability, there should be corresponding excited states that cause the instability of the reference confi guration. The electronic control of the instabilities via vibronic coupling has been considered in detail in a series of papers [4][5][6][7][8][9][10][11][12][13].One of the examples of electronic control on nuclear confi guration instability is the stabilization of vertically excited states. The available experimental and theoretical data indicate that in the electronically excited states molecules may adopt equilibrium geometries very different from those in the ground states. Moreover, the distortions of some molecules in the lowest triplet state are stronger than in the excited singlet state of the same symmetry. In [14] the pseudo Jahn-Teller effect was used to explain the origin of the carbo...

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Recent Developments in the Jahn–Teller Effect Theory

Берсукер

2009

Springer Series in Chemical Physics

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In a review paper an updated formulation of the Jahn-Teller (JT) effect (JTE) (including proper JT, pseudo JT, and Renner-Teller (RT) effects) is given based on the latest achievements in this field, including the conclusion that the JTE is the only source of instability and distortion of any polyatomic system from its high-symmetry configuration. Together with the statement in particle physics that "symmetry breaking is always associated with a degeneracy" the extended formulation of the JTE leads us to the speculation that Nature tends to avoid degeneracies. In the updated formulation the presence of two or more electronic states, degenerate or within a limited energy gap, that mix strongly enough under nuclear displacements is the necessary and sufficient condition of instability. Distinguished from the usually considered electron-vibrational (electron-phonon) interaction in which one electronic state interacts with totally symmetric vibrations, the JTE, mixing two or more electronic states, involves also low-symmetry displacements.It is shown that if in the global minimum of the adiabatic potential energy surface (APES) the polyatomic system is distorted from its high-symmetry configuration, while the electronic term in the latter is neither degenerate nor pseudo degenerate, and hence there is no apparent JTE or pseudo-JTE (PJTE), the distortion is due to these effects in the higher excited states. This is possible when the JT stabilization energy is larger than the energy gap to the ground state. Since the JT origin of the distortion is not seen explicitly from the calculation of the ground state, we call it hidden JTE (HJTE). There are two kinds of HJTE: (1) induced by proper JTE in an excited state, and (2) produced by the PJTE which mixes two exited states. Both types of HJTE are confirmed by ab initio calculations of a variety of molecular systems. While the first type of HJTE is more "accidental" (ozone, O 3 , is shown to be a nice example), the second type occurs in e 2 and t 3 electron configurations and it is accompanied by orbital disproportionation, making the spin state in the global minimum different from that of the high-symmetry configuration. This in turn results in two minima of the APES with relatively close energies, but different electronic states and spin, and a spin crossover between the two minima. With the PJTE and HJTE included, the role of excited states in the analysis of structure and properties of molecular systems in the ground state becomes most important. It can be said that no full treatment of polyatomic systems is possible without involving excited states, even when the properties in the ground state are considered.

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

Cited by 20 publications

References 5 publications

On the simple determination of the self-consistent atomic charges and Madelung potentials in ionic crystals

On the simple determination of the self-consistent atomic charges and Madelung potentials in ionic crystals

Electronic Control of Molecular Configuration Instability via Vibronic Coupling. Pseudo Jahn-Teller Stabilization of Vertically Excited States of F2CO, N2H2 and H2C2O Molecules

Recent Developments in the Jahn–Teller Effect Theory

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