Abstract
We have investigated the pressure dependence of the static structure of liquid GeTe based on ab initio molecular dynamics simulations. The pressure range is between ambient pressure and 250 GPa, and their temperatures between 1000 K and 4000 K, which keep the liquid state. In this study, we found two transition stages caused by the compression. At the first stage, below 12 GPa, atomic distances elongate and Peierls-type distortion is dissolved with increasing pressure. At the second stage, above 12 GPa, atomic distances shorten and the electronic states shows metallic.
Highlights
Germanium tellurides (GeTe) are interesting materials because of their semi-conducting properties and the fast phase transition, e.g., Ge-Sb-Te
We investigate the pressure dependence of the static structure of liquid GeTe based on ab initio molecular dynamics (AIMD) simulations, in which the electronic structure is calculated in the framework of the density functional theory with the generalized gradient approximation
We have carried out the calculations by using AIMD simulations, in which the electronic states were calculated by the projector-augmented-wave (PAW) method [4,5] within the framework of the density functional theory (DFT) in which the generalized gradient approximation (GGA) [6] was used for the exchange-correlation energy
Summary
Germanium tellurides (GeTe) are interesting materials because of their semi-conducting properties and the fast phase transition, e.g., Ge-Sb-Te. Crystalline GeTe at room temperature has A7 structure, which is distorted from fcc rocksalt (B1) to expand (111) direction This distortion is named as Peierls distortion. When the temperature increases up to about 700 K, GeTe changes from A7 to B1 structure, where Ge and Te atoms are sixfold coordinated each other. When the temperature increases up to about 1000 K, crystalline GeTe melts and its coordination number becomes approximately 3-4, i.e., the Peierls-type A7 structure appears again [1]. Compression induces the structural change of crystalline GeTe. When pressure increases up to around 3 GPa, GeTe changes from A7 to rocksalt structure. It has been suggested that, under further compression, GeTe eventually becomes bcc (CsCltype) structure at 40-50 GPa, through several structural changes [2]. The temperature and pressure ranges are from 1000 to 4000 K and from 0 to 250 GPa, respectively
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