Incommensurate host-guest structures in compressed elements: Hume—Rothery effects as origin

30th International Conference on Interaction of Intense Energy Fluxes with Matter

Degtyareva, V.F.^1

Institute of Solid State Physics, Russian Academy of Sciences, Institutskaya Street 2, Chernogolovka, Moscow Region

142432, Russia^1

关键词: Alkaline-earth elements;    Brillouin zones;    Hume-Rothery phasis;    Incommensurate structure;    Modulated structures;    Structural relationship;    Structural stabilities;    Valence electron;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/653/1/012075/pdf
DOI  :  10.1088/1742-6596/653/1/012075

来源: IOP

【 摘 要 】

Discovery of the incommensurate structure in the element Ba under pressure 15 years ago was followed by findings of a series of similar structures in other compressed elements. Incommensurately modulated structures of the host-guest type consist of a tetragonal host structure and a guest structure. The guest structure forms chains of atoms embedded in the channels of host atoms so that the axial ratio of these subcells along the c axis is not rational. Two types of the host-guest structures have been found so far: with the host cells containing 8 atoms and 16 atoms; in these both types the guest cells contain 2 atoms. These crystal structures contain a non-integer number of atoms in their unit cell: tI11∗ in Bi, Sb, As, Ba, Sr, Sc and tI19∗ in Na, K, Rb. We consider here a close structural relationship of these host-guest structures with the binary alloy phase Au3Cd5-tI32. This phase is related to the family of the Hume-Rothery phases that is stabilized by the Fermi sphere-Brillouin zone interaction. From similar considerations for alkali and alkaline-earth elements a necessary condition for structural stability emerges in which the valence electrons band overlaps with the upper core electrons and the valence electron count increases under compression.