2010/06/30 by Andriy Zhugayevych, Vassiliy Lubchenko · 1 citation
Materials Science · Physics and Astronomy · #Advanced Thermoelectric Materials and Devices #Phase-change materials and chalcogenides #Quasicrystal Structures and Properties #cond-mat.dis-nn #cond-mat.mtrl-sci
paper · pdf · doi:10.1063/1.3511708
published as J. Chem. Phys. 133, 234504 (2010) · 17 pages, 15 figures, revised version, final version to appear in J. Chem. Phys
arxiv created 2010/10/18 · openalex publication_date 2010/12/16 · arxiv updated 2011/03/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We propose a structural model that treats in a unified fashion both the atomic motions and electronic excitations in quenched melts of pnictide and chalcogenide semiconductors. In Part I [A. Zhugayevych and V. Lubchenko, J. Chem. Phys. 133, 234503 (2010)], we argued these quenched melts represent aperiodic ppσ-networks that are highly stable and, at the same time, structurally degenerate. These networks are characterized by a continuous range of coordination. Here we present a systematic way to classify these types of coordination in terms of discrete coordination defects in a parent structure defined on a simple cubic lattice. We identify the lowest energy coordination defects with the intrinsic midgap electronic states in semiconductor glasses, which were argued earlier to cause many of the unique optoelectronic anomalies in these materials. In addition, these coordination defects are mobile and correspond to the transition state configurations during the activated transport above the glass transition. The presence of the coordination defects may account for the puzzling discrepancy between the kinetic and thermodynamic fragility in chalcogenides. Finally, the proposed model recovers as limiting cases several popular types of bonding patterns proposed earlier including: valence-alternation pairs, hypervalent configurations, and homopolar bonds in heteropolar compounds.