Vibrational properties of amorphous germanium under pressure and its thermal expansion and Gruneisen parameters


Durandurdu M.

JOURNAL OF NON-CRYSTALLINE SOLIDS, vol.356, pp.977-981, 2010 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 356
  • Publication Date: 2010
  • Doi Number: 10.1016/j.jnoncrysol.2010.01.028
  • Title of Journal : JOURNAL OF NON-CRYSTALLINE SOLIDS
  • Page Numbers: pp.977-981

Abstract

We study the vibrational properties of amorphous germanium at high pressures using a constant pressure ab initio technique. With the application of pressure, the low-frequency modes gradually soften with a decrease in their acoustic-like nature while the high-frequency modes shift to larger frequencies. The acoustic-like vibrations are found to have negative Gruneisen parameters whereas the optic-like ones have positive values of about +1. A negative thermal expansion is produced below 200 K. Furthermore, we find that pressure reduces the number of localized states. Accompanied by the phase transition into a metallic high-density amorphous state, the nature of the low-frequency vibrations is changed from acoustic-like to optic-like and from bond bending to bond stretching. (C) 2010 Elsevier B.V. All rights reserved.