Phosphorus Dimerization in Gallium Phosphide at High Pressure

Abstract

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.

Pressure-Induced Novel Stable Stoichiometries in Molybdenum–Phosphorus Phase Diagrams under Pressure

“…P units display various behaviors under compression, which leads to the structural diversity of MPs under high pressure. Phosphorus dimerization occurs in the high-pressure phase (super- Cmcm ) of GaP . This phase shows strong bonding differentiation and distorted fivefold coordination geometries with a single covalent P–P bond of 2.171 Å.…”

“…Phosphorus dimerization occurs in the high-pressure phase (super-Cmcm) of GaP. 25 This phase shows strong bonding differentiation and distorted fivefold coordination geometries with a single covalent P−P bond of 2.171 Å. Several substructures, such as P 2 , P 3 , and P 4 units, and a disordered "graphene-like" sublattice are found in the P-rich Mg−P system under compression.…”

Electrical Transport Properties of Gallium Phosphide under High Pressure

“…Polian and coworkers determined the pressure relationships of the three independent elastic constants of GaP up to 15 GPa using Brillouin scattering close to the reported phase transition. GaP with a super‐ Cmcm structure has also been investigated at 43 GPa and 1300 K using a combined experimental and computational approaches, which showed this structure to be more thermodynamically stable above roughly 20 GPa than previously proposed polymorphs . The electronic and optical properties of GaP under hydrostatic pressures have also been calculated using the full‐potential linear augmented plane‐wave method; this showed an increase in the anion charge causing a general decrease in the band gap, valence bandwidth, pressure coefficients, and deformation potential, whereas the reflectivity was found to have a maximum of approximately 70% .…”

“…GaP with a super-Cmcm structure has also been investigated at 43 GPa and 1300 K using a combined experimental and computational approaches, which showed this structure to be more thermodynamically stable above roughly 20 GPa than previously proposed polymorphs. [9] The electronic and optical properties of GaP under hydrostatic pressures have also been calculated using the full-potential linear augmented plane-wave method; this showed an increase in the anion charge causing a general decrease in the band gap, valence bandwidth, pressure coefficients, and deformation potential, whereas the reflectivity was found to have a maximum of approximately 70%. [10] Van Vechten [11] predicted 22 GPa as the theoretical critical pressure of transformation to the metallic phase, and Onodera et al [12] reported that the metallization transition of a GaP specimen embedded in a pyrophyllite octahedron was in the vicinity of 50 GPa using a double-stage split-sphere apparatus.…”

Excitons in InP, GaP, and GaxIn1−xP quantum dots: Insights from time-dependent density functional theory

“…Among them, InP is considered as a promising candidate to replace CdSe as a material of choice for commercial QD displays due to its low toxicity 11,12 but comparable, or even broader emission color range over traditional group II-VI compounds. The other members of group III-V family such as GaP and GaInP have also seen a significant surge of interest as light emitting materials [13][14][15][16] . Even though the synthetic chemistry of colloidal III-V semiconducting QDs has seen significant progress [17][18][19] , the growth of uniform, monodisperse high quality QDs of group III-V remains challenging.…”