Anomalous optical and electronic properties of dense sodium

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 106; no. 16; pp. 6525 - 6528
• Main Authors: Lazicki, A, Goncharov, A.F, Struzhkin, V.V, Cohen, R.E, Liu, Z, Gregoryanz, E, Guillaume, C, Mao, H.-K, Hemley, Russell J
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 21-04-2009; National Acad Sciences
• Subjects: Alkali metals; Atoms; Complex Systems: From Chemistry to Systems Biology Special Feature; Electrical phases; High pressure; Infrared reflection; Lithium; Measurement; Metals; Optical reflection; Physical Sciences; Reflectance; Sodium; Spectral reflectance; Spectrum analysis
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0902062106

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.