title: Amorphous Ge₁₅Te₈₅: density functional, high-energy x-ray and neutron diffraction study.
abstract: The structure and electronic properties of amorphous Ge(15)Te(85) have been studied by combining density functional (DF) simulations with high-energy x-ray and neutron diffraction measurements. Three models with 560 atoms have been constructed using reverse Monte Carlo methods constrained to (1) agree with the experimental structure factors S(Q), and have (2) energies close to the DF minimum and (3) a semiconducting band structure. The best structure is based on the melt-quenched DF structure and has a small number of Ge-Ge bonds. It shows interlocking networks of Te and GeTe with a significant fraction (22-24%) of voids (cavities). Ge occurs with both tetrahedral and 3 + 3 defective octahedral configurations, and the coordination of Te is slightly higher than indicated by the '8 - N rule' (N is the number of valence electrons). The GeTe network includes clusters of ABAB squares (A = Ge, B = Te), and the bonding is characterized by the chemical bond orders.
authors.affiliation: Nanoscience Center, Department of Physics, University of Jyväskylä, PO Box 35, FI-40014 Jyväskylä, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Kalikka
authors.forename: J
authors.initials: J
authors.lastname: Akola
authors.forename: R O
authors.initials: RO
authors.lastname: Jones
authors.forename: S
authors.initials: S
authors.lastname: Kohara
authors.forename: T
authors.initials: T
authors.lastname: Usuki