The Light Elements at High Pressure, in Layered Form, and in Combination

Abstract

Neutral macroscopic assemblies of nuclei and electrons are expected to take up symmetric structures at sufficiently high pressures. On systematic reduction of pressure electronic bound states appear (ion formation) and with them, by a Jahn-eller argument, the onset of less symmetric structures including those with a layered character. Pauli exclusion of the remaining electrons can lead to valence states with quite non-uniform densities, examples from the alkalis being given. Electron-ion coupling can be strong, and combined with high electronic densities of states, the prospect of electron pairing arises, as it does in the light elements in combination (e.g., MgB ₂) Pressure studies of superconductivity offer a quite general prospect for elucidating the relative roles of effective electron-electron and electron-phonon coupling in this pairing. Boron offers particular promise for further high pressure study, not only with respect to its superconductivity, but also in liquid phase at high pressure

This work has been supported by the National Science Foundation