Keywords :
Theoretical or Mathematical/ ab initio calculations; density; germanium alloys; liquid semiconductors; molecular dynamics method; tellurium alloys; thermal expansion/ Te-rich liquid germanium tellurides; density anomaly; ab initio molecular dynamics calculations; Brillouin zone; chalcogenides; negative thermal expansion; Peierls-like mechanism; 633 to 733 K; Ge 0.15Te 0.85/ A6120J Computer simulation of static and dynamic liquid behaviour A6570 Thermal expansion and thermomechanical effects/ temperature 6.33E+02 to 7.33E+02 K/ Ge0.15Te0.85/bin Ge0.15/bin Te0.85/bin Ge/bin Te/bin
Abstract :
[en] The density anomaly of liquid Ge 0.15Te 0.85 measured between 633 and 733 K is investigated with ab initio molecular dynamics calculations at four temperatures and at the corresponding experimental densities. For box sizes ranging from 56 to 112 atoms, an 8 k-points sampling of the Brillouin zone is necessary to obtain reliable results. Contrary to other Ge chalcogenides, no sp 3 hybridization of the Ge bonding is observed. As a consequence, the negative thermal expansion of the liquid is not related to a tetrahedral bonding as in the case of water or silica. We show that it results from the symmetry recovery of the local environment of Ge atoms that is distorted at low temperature by a Peierls-like mechanism acting in the liquid state in the same way as in the parent solid phases
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