Anomalous optical and electronic properties of dense sodium.

Lazicki, A; Goncharov, A F; Struzhkin, V V; Cohen, R E; Liu, Z; Gregoryanz, E; Guillaume, C; Mao, H-K et al. · Proc Natl Acad Sci U S A · 2009

basic_science · Level V

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Abstract

Synchrotron infrared spectroscopy on sodium shows a transition from a high reflectivity, nearly free-electron metal to a low-reflectivity, poor metal in an orthorhombic phase at 118 GPa. Optical spectra calculated within density functional theory (DFT) agree with the experimental measurements and predict a gap opening in the orthorhombic phase at compression beyond its stability field, a state that would be experimentally attainable by appropriate choice of pressure-temperature path. We show that a transition to an incommensurate phase at 125 GPa results in a partial recovery of good metallic character up to 180 GPa, demonstrating the strong relationship between structure and electronic properties in sodium.