Structure, electronic, and vibrational properties of glassy Ga 11Ge 11Te 78

Experimentally constrained density functional study

I. Voleská, J. Akola, P. Jóvári, J. Gutwirth, T. Wágner, Th Vasileiadis, S. N. Yannopoulos, R. O. Jones

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

The atomic structure and electronic and vibrational properties of glassy Ga 11Ge 11Te 78 have been studied by combining density functional (DF) simulations with x-ray (XRD) and neutron diffraction (ND), extended x-ray absorption fine structure (EXAFS), and Raman spectroscopies. The final DF structure (540 atoms) was refined using reverse Monte Carlo methods to reproduce the XRD and ND data as well as Ge and Ga K-edge EXAFS spectra, while maintaining a semiconducting band gap and a total energy close to the DF minimum. The local coordination of Ga is tetrahedral, while Ge has twice as many tetrahedral as defective octahedral configurations. The average coordination numbers are Ga, 4.1, Ge, 3.8, and Te, 2.6. The chemical bonding around Ga involves Ga 4s, Ga 4p, Te 5s, and Te 5p orbitals, and the bond strengths show bonding close to covalent, as in Ge. There are fewer Te chains and cavities than in amorphous Te, and a prepeak in the structure factor at 1.0 Å -1 indicates medium-range order of the Ga/Ge network. Density functional calculations show that contributions of Te-Te, Ga-Te, and Ge-Te bonds dominate the experimental Raman spectra in the 110-150 cm -1 range.

Original languageEnglish
Article number094108
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume86
Issue number9
DOIs
Publication statusPublished - Sep 13 2012

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Electronic structure
Neutron diffraction
electronic structure
X rays
x ray absorption
neutron diffraction
fine structure
Density functional theory
Raman spectroscopy
Raman scattering
Energy gap
Monte Carlo methods
coordination number
atomic structure
Monte Carlo method
Atoms
x ray diffraction
Raman spectra
orbitals
cavities

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

Structure, electronic, and vibrational properties of glassy Ga 11Ge 11Te 78 : Experimentally constrained density functional study. / Voleská, I.; Akola, J.; Jóvári, P.; Gutwirth, J.; Wágner, T.; Vasileiadis, Th; Yannopoulos, S. N.; Jones, R. O.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 86, No. 9, 094108, 13.09.2012.

Research output: Contribution to journalArticle

Voleská, I. ; Akola, J. ; Jóvári, P. ; Gutwirth, J. ; Wágner, T. ; Vasileiadis, Th ; Yannopoulos, S. N. ; Jones, R. O. / Structure, electronic, and vibrational properties of glassy Ga 11Ge 11Te 78 : Experimentally constrained density functional study. In: Physical Review B - Condensed Matter and Materials Physics. 2012 ; Vol. 86, No. 9.
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