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

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

29 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 - 13 Sep 2012
MoE publication typeA1 Journal article-refereed

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