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Title: Thermal properties of CaMoO{sub 4}: Lattice dynamics and synchrotron powder diffraction studies

Abstract

The structure of calcium molybdate was studied by means of synchrotron based high-resolution powder diffraction methods in the temperature range 12-300 K. The scheelite structure type was confirmed for CaMoO{sub 4} in the temperature region investigated and no structural anomalies were observed. Thermal expansion coefficients extracted from the thermal dependencies of the cell sizes are found to be in good agreement with the predictions from our lattice dynamics calculations that form the background for microscopic interpretation of the experimental data. From the analyses of experimental results and the calculated thermal expansion coefficients, elastic constants, phonon density of states, heat capacities, entropy, and Grueneisen parameters it is concluded that a quasiharmonic lattice dynamics approach provides a good description of these properties for CaMoO{sub 4} at temperatures below 800 K.

Authors:
; ; ; ;  [1];  [2];  [3];  [4]
  1. Institute for Material Science, Darmstadt University of Technology, Petersenstrasse 23, Darmstadt D-64287 (Germany)
  2. (United Kingdom)
  3. (Ukraine)
  4. (Germany)
Publication Date:
OSTI Identifier:
20787813
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 73; Journal Issue: 1; Other Information: DOI: 10.1103/PhysRevB.73.014104; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CALCIUM COMPOUNDS; CRYSTAL STRUCTURE; DIFFRACTION METHODS; ENERGY-LEVEL DENSITY; ENTROPY; MOLYBDATES; PHONONS; POWDERS; SPECIFIC HEAT; TEMPERATURE DEPENDENCE; THERMAL EXPANSION; X-RAY DIFFRACTION

Citation Formats

Senyshyn, A., Kraus, H., Mikhailik, V. B., Vasylechko, L., Knapp, M., Physics Department, University of Oxford, Keble Road, Oxford OX1 3RH, Lviv Polytechnic National University, 12 Bandera Street, Lviv 79013, and Institute for Material Science, Darmstadt University of Technology, Petersenstrasse 23, Darmstadt D-64287. Thermal properties of CaMoO{sub 4}: Lattice dynamics and synchrotron powder diffraction studies. United States: N. p., 2006. Web. doi:10.1103/PHYSREVB.73.0.
Senyshyn, A., Kraus, H., Mikhailik, V. B., Vasylechko, L., Knapp, M., Physics Department, University of Oxford, Keble Road, Oxford OX1 3RH, Lviv Polytechnic National University, 12 Bandera Street, Lviv 79013, & Institute for Material Science, Darmstadt University of Technology, Petersenstrasse 23, Darmstadt D-64287. Thermal properties of CaMoO{sub 4}: Lattice dynamics and synchrotron powder diffraction studies. United States. doi:10.1103/PHYSREVB.73.0.
Senyshyn, A., Kraus, H., Mikhailik, V. B., Vasylechko, L., Knapp, M., Physics Department, University of Oxford, Keble Road, Oxford OX1 3RH, Lviv Polytechnic National University, 12 Bandera Street, Lviv 79013, and Institute for Material Science, Darmstadt University of Technology, Petersenstrasse 23, Darmstadt D-64287. Sun . "Thermal properties of CaMoO{sub 4}: Lattice dynamics and synchrotron powder diffraction studies". United States. doi:10.1103/PHYSREVB.73.0.
@article{osti_20787813,
title = {Thermal properties of CaMoO{sub 4}: Lattice dynamics and synchrotron powder diffraction studies},
author = {Senyshyn, A. and Kraus, H. and Mikhailik, V. B. and Vasylechko, L. and Knapp, M. and Physics Department, University of Oxford, Keble Road, Oxford OX1 3RH and Lviv Polytechnic National University, 12 Bandera Street, Lviv 79013 and Institute for Material Science, Darmstadt University of Technology, Petersenstrasse 23, Darmstadt D-64287},
abstractNote = {The structure of calcium molybdate was studied by means of synchrotron based high-resolution powder diffraction methods in the temperature range 12-300 K. The scheelite structure type was confirmed for CaMoO{sub 4} in the temperature region investigated and no structural anomalies were observed. Thermal expansion coefficients extracted from the thermal dependencies of the cell sizes are found to be in good agreement with the predictions from our lattice dynamics calculations that form the background for microscopic interpretation of the experimental data. From the analyses of experimental results and the calculated thermal expansion coefficients, elastic constants, phonon density of states, heat capacities, entropy, and Grueneisen parameters it is concluded that a quasiharmonic lattice dynamics approach provides a good description of these properties for CaMoO{sub 4} at temperatures below 800 K.},
doi = {10.1103/PHYSREVB.73.0},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 1,
volume = 73,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • The A V{sub 2}O{sub 4} (A=Mg{sup 2+}, Zn{sup 2+}, Cd{sup 2+}) spinels are three-dimensional spin-1 frustrated systems with orbital degree of freedom, which have been known to possess intriguing orbital states causing releases of spin frustration at low temperatures. We have performed synchrotron X-ray and convergent beam electron diffraction measurements for one of these vanadates, MgV{sub 2}O{sub 4} in order to clarify its crystal structure in the high temperature cubic phase, which is regarded as an important starting point for understanding the details of the low temperature phase. We have successfully observed that the [001] zone axis convergent beam electronmore » diffraction pattern exhibits 4mm symmetry, suggesting the space group of Fd3{sup ¯}m in the cubic MgV{sub 2}O{sub 4}. It has also been demonstrated that the crystal structure of the cubic MgV{sub 2}O{sub 4} contains VO{sub 6} octahedra elongated along the threefold rotation axis. Based on our results, we discuss the orbital states of MgV{sub 2}O{sub 4} as well as the other spinel vanadates. - Graphical abstract: Precise geometry of the VO{sub 6} octahedra in the cubic phase of MgV{sub 2}O{sub 4} spinel determined with the synchrotron powder XRD data. - Highlights: • We examined the crystal structure of the cubic phase of MgV{sub 2}O{sub 4} spinel. • We prepared the single crystal and powdered sample of MgV{sub 2}O{sub 4} with high quality. • The result of the CBED measurement agrees with the space group of Fd3{sup ¯}m in the phase. • The cubic phase has VO{sub 6} octahedra elongated along the threefold rotation axis.« less
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