Sodium: a charge-transfer insulator at high pressures

Abstract

By means of first-principles methods we analyze the optical response of transparent dense sodium as a function of applied pressure. We discover an unusual kind of charge-transfer exciton that proceeds from the interstitial distribution of valence electrons repelled away from the ionic cores by the Coulomb interaction and the Pauli repulsion. The predicted absorption spectrum shows a strong anisotropy with light polarization that just at pressures above the metal-insulator transition manifests as sodium being optically transparent in one direction but reflective in the other. This result provides a key information about the crystal structure of transparent sodium, a new unconventional inorganic electride.

revtex4, 5+8 pages

References in corpus (3)

• Transparent dense sodium
• {\it Ab--initio} finite temperature excitons
• Interstitial Electronic Localization

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