Energy loss spectra of lithium under pressure

Abstract

According to the nearly free-electron-like approximation, electrons in alkaline metals are expected to be delocalized under pressure. However, recent theoretical and experimental results strikingly indicate the opposite behavior. For example, under pressure electronic band structure flattens anisotropically and increases the covalent character of alkaline metals, which induces the observed complexities in these systems. Specially considering that even at ambient pressure the observed anomalous features in the loss spectra of lithium cannot be explained within the nearly free-electron-like model, these additional anomalies under pressure are also expected to strongly modify its dynamic electronic response function. In this paper, we present ab initio calculations of the energy-loss spectra of lithium up to 40 GPa. Besides analyzing the dispersion of the new type of plasmons arising in lithium under pressure, the role of band structure versus crystal local field effects and exchange correlation has also been investigated.