Computational Study Of Four-Fold Coordinate Boron In Borates: Assignment Of Dge-Shared Structures

Several issues raised by the recent discovery of compounds with four-fold coordinate boron in edge-shared pairs are addressed by means of first principles computations. First, site-specific assignments are made by computing the quadruple coupling of each boron and comparing literature values. Then, the bonding contacts in this unusual arrangement are studied through the atoms-in-molecules approach. Finally, the unusual three-fold coordinate oxygen in another high pressure borate phase is studied in the same way. All computations were performed using the projector-augmented wave formalism.