Crystal Structure of Luminescent ZnSiP2

Abstract

ZnSiP2 crystallizes with the chalcopyrite structure: there is no detectable difference in x-ray scattering between luminescent and nonluminescent crystals. The level of impurity, either in the form of chemical dopant, physical defect, or a departure of less than about 1% from complete order at the Zn and Si sites hence determines if the crystal luminesces or not on excitation by an electron beam. The lattice constants of this tetragonal crystal at 298°K are a = 5.399 ± 0.001 and c = 10.435 ± 0.002 Å. The space group is I4̄2d, and there are four formulas in the unit cell. A total of 2023 reflections were measured with the luminescent crystal, and 1600 with the nonluminescent crystal, using pexrad. The final agreement factor, based on a combination of 197 symmetry-independent reflections from the first crystal and 176 from the second, is 0.049. Each Zn is tetrahedrally surrounded by 4 P atoms at 2.375 ± 0.001 Å distance, and each Si by 4 P atoms at 2.254 ± 0.001 Å. All phosphorus tetrahedra have four P–P edges of length 3.832 ± 0.002 Å. The two remaining independent P–P edges are of 3.968 ± 0.001 Å distance in the ZnP4 tetrahedra, and are of 3.684 ± 0.001 Å in the SiP4 tetrahedra.