Crystal and electronic structure of La3Zn2−xP4 – New phosphide with isolated P3− species

The new phosphide La3Zn2−xP4 was synthesized from lanthanum, LaZn and red phosphorous in a NaCl/KCl halide flux at 1120 K. La3Zn2−xP4 crystallizes with a new structure type: R3¯m, a = 418.72(7), c = 4143.7(1) pm, wR2 = 0.0577, 1061 F2 values for La3Zn1.75P4 and a = 418.99(6), c = 4157.1(8) pm, wR2 = 0.0485, 337 F2 values for La3Zn1.88P4 with 17 variables per refinement. The P3− phosphide anions show an hhcc stacking sequence, similar to the structures of Mg3In and PuGa3. The Zn2+ and La3+ cations fill 1/4 and 3/4 of the tetrahedral and octahedral voids, respectively, in an ordered manner, leading to a layer of ZnP4 tetrahedra and triple layers of LaP6 octahedra. DFT band structural calculations verify that the lower zinc occupation stabilizes the structure close to an electron precise composition.

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