Publications Details

Phosphorus Dimerization in Gallium Phosphide at High Pressure

Lavina, Barbara; Kim, Eunja; Cynn, Hyunchae; Weck, Philippe F.; Seaborg, Kelly; Siska, Emily; Meng, Yue; Evans, William

Using combined experimental and computational approaches, we show that at 43 GPa and 1300 K gallium phosphide adopts the super-Cmcm structure, here indicated with its Pearson notation oS24. First-principles enthalpy calculations demonstrate that this structure is more thermodynamically stable above ∼20 GPa than previously proposed polymorphs. In contrast to other polymorphs, the oS24 phase shows a strong bonding differentiation and distorted fivefold coordination geometries of both P atoms. The shortest bond of the phase is a single covalent P-P bond measuring 2.171(11) Å at synthesis pressure. Phosphorus dimerization in GaP sheds light on the nature of the super-Cmcm phase and provides critical new insights into the high-pressure polymorphism of octet semiconductors. Bond directionality and anisotropy explain the relatively low symmetry of this high-pressure phase.