From Wade-Mingos to Zintl-Klemm at 100 GPa: Binary Compounds of Boron and Lithium

Structural diversity and a variety: of bonding schemes' emerge as characteristics of the Li-B phase diagram, in this ground state :theoretical investigation. We studied stoichiometries ranging from LiB15 to Li5B, over a pressure range from 1 atm to 300 GPa. At P = 1 atm, stability is found for the experimentally known LiB0.8-1.0, LiB3, and Li3B14 phases As the pressure rises, the latter two structures are no longer even metastable, while the LiB0.8-1.0 structures. Change in geometry and narrow their range of off-stoichiometry, eventually coming at high pressure to a diamondoid NaTl-type LiB. This phase then dominates the convex hull of stabiliti. Other phases emerge as stable points at some pressure: LiB4, Li3B2, Li2B, and Li5B. At the boron-rich end, one. obtains structures expectedly containing..polyhedral motifs, and geometries are governed by Wade-Mingos electron counts; LiB4 has a BaAl4 structure. In the center and on the lithium-rich side of phase diagram, Zintl-phase considerations, i.e., bonding between Bn- entities, give us insight into the structures-tetrahedral B- networks in LiB; B pairs to isolated bonds in Li5B.