Elucidation of the Off-Center Displaced Mo in Octahedral Coordination in Ba2MoO5
Andries van Hattem (TU Delft - RST/Reactor Physics and Nuclear Materials)
L.M.T. de Geus (TU Delft - RST/Reactor Physics and Nuclear Materials)
A. Sacristán Civera (TU Delft - RST/Reactor Physics and Nuclear Materials)
Robert Dankelman (TU Delft - RID/TS/Technici Pool)
S.D. Couweleers (TU Delft - RST/Technici Pool)
Christoph Hennig (European Synchrotron Radiation Facility (ESRF))
Jean Christophe Griveau (European Commission Joint Research Centre)
Rudy J.M. Konings (TU Delft - RST/Reactor Physics and Nuclear Materials)
Anna L. Smith (TU Delft - RST/Reactor Physics and Nuclear Materials)
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Abstract
The detailed crystal structure as well as the heat capacity at low temperature and standard entropy of Ba2MoO5 are reported for the first time. High-resolution X-ray and neutron diffraction were employed to reveal the structural features of this compound. Ba2MoO5 has a six-coordinated Mo and a strongly negative excess volume with respect to the binary oxides. X-ray absorption near edge structure (XANES) spectroscopy at the Mo K-edge shows Mo to be in the oxidation state 6+. The pre-edge peak in the XANES spectrum indicates a distorted octahedral environment, in line with the results from diffraction studies and FDMNES calculations. The standard entropy and heat capacity of Ba2MoO5 at 298.15 K, determined with a thermal-relaxation technique, are calculated to be respectively 223.2 ± 7 and 184.7 ± 5 J·K–1·mol–1. The obtained thermodynamic properties are discussed in the context of the literature reports on molybdate compounds.
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