Infrared and Raman spectra of the elpasolites Cs"2NaSbCl"6 and Cs"2NaBiCl"6: Evidence for a pseudo Jahn-Teller distorted ground state

The infrared and Raman spectra of the elpasolites Cs"2NaSbCl"6 and Cs"2NaBiCl"6 provide evidence for a dynamically distorted electronic ground state of the MCl^3^-"6 (M = Sb^3^+, Bi^3^+) octahedra. Broad T"1"u absorption bands in the infrared (IR) spectra indicate that vibronic coupling between the ... Ausführliche Beschreibung

1. Person: Smit, W.M.A.
Weitere Personen: Dirksen, G.J.; Stufkens, D.J.
Quelle: in Journal of Physics and Chemistry of Solids Vol. 51, No. 2 (1990), p. 189-196
Weitere Artikel
Format: Online-Artikel
Genre: IR, Raman, elpasolites, antimony, bismuth, pseudo Jahn-Teller effect
Sprache: English
Veröffentlicht: 1990
Beschreibung: Online-Ressource
Online Zugang: Online
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Anmerkung: Copyright: Copyright (c) 2002 Elsevier Science Ltd
Zusammenfassung: The infrared and Raman spectra of the elpasolites Cs"2NaSbCl"6 and Cs"2NaBiCl"6 provide evidence for a dynamically distorted electronic ground state of the MCl^3^-"6 (M = Sb^3^+, Bi^3^+) octahedra. Broad T"1"u absorption bands in the infrared (IR) spectra indicate that vibronic coupling between the A"1"g ground state and the lower T"1"u excited states leads to structural fluctuations with a time scale of the order of the vibrational time scale. The Raman spectrum of Cs"2NaBiCl"6 shows that on the time scale of electronic transitions the structure of the BiCl^3^-"6 anion is (nearly) octahedral, whereas in the case of Cs"2NaSbCl"6 the Raman spectrum reveals a more strongly distorted octahedral structure for the SbCl^3^-"6 anion with C"2"x and C"3"v characteristics which are easily generated by linear combinations of the T"1"u stretching and bending coordinates. The pseudo Jahn-Teller distortions are induced by the s^2 electronic configuration of the Sb^3^+ and Bi^3^+ ions. The tendency to accommodate the s^2 electrons in a lone pair orbital seems to be counteracted by the high symmetry crystal field which forces the s^2 electrons to occupy an s-type antibonding orbital. This is reflected by the relatively large values for the effective Sb^3^+ and Bi^3^+ ionic radii in these compounds.
ISSN: 0022-3697

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