Experimental and Theoretical Electronic Structure Investigations on -Nb3Cl8 and the Intercalated Phase ![]()
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- 作者：John Rory Kennedy ; Peter Adler ; Richard Dronskowski ; and Arndt Simon
- 刊名：Inorganic Chemistry
- 出版年：1996
- 出版时间：April 10, 1996
- 年：1996
- 卷：35
- 期：8
- 页码：2276 - 2282
- 全文大小：229K
- 年卷期：v.35,no.8(April 10, 1996)
- ISSN：1520-510X
文摘
The electronic structures of the cluster compound
-Nb3Cl8 and the intercalated phase
'-NaNb3Cl8 have beenstudied by core level and valence band X-ray and ultravioletphotoelectron spectroscopy (XPS and UPS), diffusereflectance spectroscopy, and charge-self-consistent molecular orbital(CSC-EH) and band structure (CSC-EH-TB) calculations. The crystal structures of the two compoundsconsist of layers of interconnectedNb3Cl13 units.XP and UP valence band spectra as well as the band structurecalculations show well separated sets of Cl 3plevels at lower energy (higher binding energy) and Nb 4d levels athigher energy (lower binding energy), indicativeof mainly ionic Nb-Cl bonding. The UP spectra of-Nb3Cl8 reveal a triple-peak structurefor the Nb 4d levels,corresponding to the 1a1, 1e, and 2a1metal-metal bonding orbitals of a seven-electron Nb3cluster as suggestedby theory. The valence band shapes are in good agreement with thetheoretical density-of-states curve. Therelative intensities in the XP valence band spectra of'-NaNb3Cl8 evidence an additionalelectron in the Nb 4dorbitals. The better resolved UP spectra, however, show a broadpattern for the Nb 4d levels which is neitherexpected from a single cluster model nor given by the theoreticaldensity-of-states curve. Possible origins forthis discrepancy between experiment and theory are discussed.Electrostatic interactions between Na+ andCl-ions in '-NaNb3Cl8 lead to a narrowingof the Cl 2p core level and Cl 3p valence band signals, the formerbeingshifted to higher binding energy in comparison to-Nb3Cl8. Two rather narrowabsorptions in the optical spectraof -Nb3Cl8 are assigned to thetransitions from the 1a1 and 1e levels into the singlyoccupied 2a1 orbital. Theseabsorptions are missing in the optical spectra of'-NaNb3Cl8, in agreement with thetheoretical expectations foran eight electron Nb3 cluster.
-Nb3Cl8 and the intercalated phase'-NaNb3Cl8 have beenstudied by core level and valence band X-ray and ultravioletphotoelectron spectroscopy (XPS and UPS), diffusereflectance spectroscopy, and charge-self-consistent molecular orbital(CSC-EH) and band structure (CSC-EH-TB) calculations. The crystal structures of the two compoundsconsist of layers of interconnectedNb3Cl13 units.XP and UP valence band spectra as well as the band structurecalculations show well separated sets of Cl 3plevels at lower energy (higher binding energy) and Nb 4d levels athigher energy (lower binding energy), indicativeof mainly ionic Nb-Cl bonding. The UP spectra of-Nb3Cl8 reveal a triple-peak structurefor the Nb 4d levels,corresponding to the 1a1, 1e, and 2a1metal-metal bonding orbitals of a seven-electron Nb3cluster as suggestedby theory. The valence band shapes are in good agreement with thetheoretical density-of-states curve. Therelative intensities in the XP valence band spectra of'-NaNb3Cl8 evidence an additionalelectron in the Nb 4dorbitals. The better resolved UP spectra, however, show a broadpattern for the Nb 4d levels which is neitherexpected from a single cluster model nor given by the theoreticaldensity-of-states curve. Possible origins forthis discrepancy between experiment and theory are discussed.Electrostatic interactions between Na+ andCl-ions in '-NaNb3Cl8 lead to a narrowingof the Cl 2p core level and Cl 3p valence band signals, the formerbeingshifted to higher binding energy in comparison to-Nb3Cl8. Two rather narrowabsorptions in the optical spectraof -Nb3Cl8 are assigned to thetransitions from the 1a1 and 1e levels into the singlyoccupied 2a1 orbital. Theseabsorptions are missing in the optical spectra of'-NaNb3Cl8, in agreement with thetheoretical expectations foran eight electron Nb3 cluster.