Be5Pt: a relativistic semiconductor

September 10, 2019

The question of how semiconducting phases may result from the union of exclusively metallic elements is an interesting and highly relevant one that furthers our understanding of bonding and valence in intermetallic compounds.

Indeed, by combining an elaborated experimental characterization with a theoretical analysis of the chemical bonding, we find semiconducting behavior (bandgap of 190 meV) for the intermetallic compound Be5Pt at a very low valence electron count.

Figure 1. Electrical resistivity of Be5Pt: (a) shape of the micro scale device used for measurement (V and I are contacts for voltage and current, respectively); (b) temperature dependence of electrical resistivity for the micro-scale specimen; inset shows Arrhenius plot of ln r vs. 1/T with linear fit (black line).

The appearance of the gap in the band structure is a consequence of relativistic effects and the unique chemical bonding picture of the compound characterized by polar two-atomic Pt-Be1 and multi-atomic Pt-Be2 bonds. Quantum chemical analysis shows strong charge transfer from Be to Pt, and reveals a three-dimensional entity of vertex-condensed empty Be4 tetrahedra with multi-center cluster bonds interpenetrated by the framework of Pt-filled vertex-condensed B4 tetrahedra with two-center polar Be-Pt bonds.

Figure 2. General bomding picture in Be5Pt with interpenetrating networks of multi-atomic (Be2-Pt, green-orange-pink) and polar two-atomic (Be1-Pt, red) interactions.

Andreas Leithe-Jasper /ALJ ; Juri Grin / JG

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