ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
The valence-contrast diffraction method is used at the Nb K edge in the analysis of the mixed-valence solid NbSe3. The NbSe3 structure consists of three parallel chains of prismatically coordinated Nb atoms and undergoes two low-temperature Peierls-type phase transitions that lead to modulated structures. Previous analysis of synchrotron-radiation single-crystal data has shown that the transition that occurs on cooling at 145 K (leading to the q1-type modulation) involves displacements of NbIII atoms as well as of some of the coordinated Se atoms, while the second transition (the q2-type modulation), at 59 K, involves displacements of NbI atoms and an Se atom of column II [van Smaalen, de Boer, Meetsma, Graafsma, Sheu, Darovskikh, Coppens & Levy (1992). Phys. Rev. B, 45, 3103–3106]. The present room-temperature study, performed at seven different wavelengths in the vicinity of the Nb absorption edge, shows the NbII-atom edge to be shifted to higher energies by about 5 eV relative to those of the other Nb atoms. This indicates a smaller population of the NbII-atom conduction band, in agreement with band structure calculations but not with conclusions derived from nuclear magnetic resonance measurements.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0108767392011279
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