6533b861fe1ef96bd12c4627

RESEARCH PRODUCT

Binary alloys of Ge and Te: order, voids, and the eutectic composition

subject

description

The liquid and amorphous structures of ${\mathrm{Ge}}_{0.15}{\mathrm{Te}}_{0.85}$ and GeTe alloys are characterized using combined density functional/molecular dynamics simulations. Te is threefold coordinated, in contrast with predictions of the ``8-$N$ rule,'' and Ge atoms (fourfold coordinated) show octahedral and tetrahedral bonding angles. Cubic local environment occurs in both materials, and GeTe shows a pronounced alternation of atomic types. Tetrahedral Ge coordination is more common in the eutectic ${\mathrm{Ge}}_{0.15}{\mathrm{Te}}_{0.85}$, which comprises corner- and edge-sharing ${\mathrm{GeTe}}_{4}$ units surrounded by Te. There is no Te segregation, and the material resembles neither GeTe nor Te. The ubiquitous cavities (voids) have been overlooked in ${\mathrm{Ge}}_{0.15}{\mathrm{Te}}_{0.85}$, where they comprise over 25% of the volume.