Structural and electronic properties of the alkali metal incommensurate phases

Alkali elements form extremely complicated structures under pressure, involving two interpenetrating, incommensurate lattices. The mechanism that stabilizes these structures is not known. In this work, the authors use density functional theory calculations to examine several possible options. After demonstrating that the calculations can capture quite subtle structural changes across the different elements, they show that in all cases the respective host structures combine two types of electride behavior: fully localized electron pairs and electrons partially localized along 1D wells. The guest atoms are seen to aid the structural formation by providing additional electronic charge and optimizing the overall packing density