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Title: Yttrium aluminium garnet under pressure: Structural, elastic, and vibrational properties from ab initio studies

The structural, elastic, and vibrational properties of yttrium aluminum garnet Y{sub 3}Al{sub 5}O{sub 12} are studied under high pressure by ab initio calculations in the framework of the density functional theory. The calculated ground state properties are in good agreement with the available experimental data. Pressure dependences of bond length and bulk moduli of the constituent polyhedra are reported. The evolution of the elastic constants and the major elastic properties, Young and shear modulus, Poisson's ratios, and Zener anisotropy ratio, are described. The mechanical stability is analyzed, on the light of “Born generalized stability criteria,” showing that the garnet is mechanically unstable above 116 GPa. Symmetries, frequencies, and pressure coefficients of the Raman-active modes are discussed on the basis of the calculated total and partial phonon density of states, which reflect the dynamical contribution of each atom. The relations between the phonon modes of Y{sub 3}Al{sub 5}O{sub 12} and the internal and external molecular modes of the different polyhedra are discussed. Infrared-active modes, as well as the silent modes, and their pressure dependence are also investigated. No dynamical instabilities were found below 116 GPa.
Authors:
 [1] ; ;  [1] ;  [2]
  1. Departamento de Física and MALTA Consolider Team, Universidad de La Laguna, 38200 San Cristóbal de La Laguna, Santa Cruz de Tenerife (Spain)
  2. (Spain)
Publication Date:
OSTI Identifier:
22493115
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 118; Journal Issue: 24; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ALUMINIUM OXIDES; ANISOTROPY; BOND LENGTHS; DENSITY FUNCTIONAL METHOD; DENSITY OF STATES; ELASTICITY; EXPERIMENTAL DATA; FERRITE GARNETS; GROUND STATES; PHONONS; POISSON RATIO; PRESSURE COEFFICIENT; PRESSURE DEPENDENCE; PRESSURE RANGE GIGA PA; PRESSURE RANGE MEGA PA 10-100; SHEAR; STABILITY; YOUNG MODULUS; YTTRIUM COMPOUNDS