Optical zone-centre phonon modes and macroscopic elasticity in hcp metals

• Published in: Solid state communications Vol. 115; no. 7; pp. 335 - 339
• Main Authors: Olijnyk, H., Jephcoat, A.P.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-01-2000; Elsevier
• Subjects: A. Metals; Applied sciences; Condensed matter: structure, mechanical and thermal properties; D. Elasticity; D. Phase transitions; D. Phonons; E. Strain, high pressure; Exact sciences and technology; Lattice dynamics; Metals. Metallurgy; Phonon states and bands, normal modes, and phonon dispersion; Phonons and vibrations in crystal lattices; Physics; D. Phase transitions; D. Phonons; E. Strain, high pressure; D. Elasticity; A. Metals; Elastic constants; Pressure effects; Lattice dynamics; Metals; Phonon mode; Grueneisen constant; Force constants; Theoretical study; HCP lattices
• ISSN: 0038-1098; 1879-2766
• DOI: 10.1016/S0038-1098(00)00207-6

A simple relation between zone-centre optical phonon modes and elastic constants for hcp metals derived previously from lattice dynamical force constant models using central and angular interactions is found to be reasonably valid for elemental metals with low elastic anisotropy. Application of this formalism to high-pressure phonon frequency data implies that phase transitions from hcp to Sm-type and to the ω-phase in the regular lanthanides and Zr, respectively, involve softening of the elastic constant
C
44, and that the rapid decrease under compression of an “unusual” high ambient-pressure TO mode Grüneisen parameter in Zn is related to the gradual transition from anisotropic→isotropic compressional behaviour with increasing pressure.