Comparative analysis for the behavior of beryllium and magnesium crystals at ultrahigh pressures

Abstract

The paper presents ab initio results on the structural phase stability of beryllium and magnesium crystals under high and ultrahigh pressures (multi-terapascal regime). Magnesium is shown to undergo a number of structural transformations which markedly reduce the crystal packing factor. As for beryllium, its high-pressure body-centered cubic phase remains stable even under ultrahigh pressures. Changes in the electronic structure of Be and Mg crystals under compression are analyzed and some interesting effects are revealed. Specifically, a narrow band gap appears in the electronic structure of magnesium under pressures above 2.5 TPa. For the metals of interest, PT-diagrams are constructed and compared with available experimental and theoretical results from other investigations.