Synthesis, structural and physical properties of new ternary metal-rich phosphides M3Ge2P (M = Mo and W)

We report on the successful synthesis of two new ternary metal-rich phosphides Mo3Ge2P and W3Ge2P, and on their structural, electrical, magnetic, thermal and electronic properties. Mo3Ge2P is thermally stable below 1500 degrees C, while W3Ge2P decomposes initially at 1110 degrees C and finally evolves into W, Ge, and P above 1360 degrees C. They adopt a non-centrosymmetric orthorhombic structure with space group C2v16 -Ama2 (No. 40). In the unit cell with content Z = 4, Mo (W) atoms are located at two inequivalent sites, respectively 4b (Mo1/W1) and 8c (Mo2/W2) Wyckoff positions, Ge and P atoms occupy 8c and 4b positions, respectively. The structure is made up of networks organized by edge-shared (Mo1/W1)3P3 planar six-membered rings and edge-shared (Mo2/W2)3Ge3 chair-form six-membered rings. Both compounds exhibit weak magnetism and metallic conduction with electron -dominant charge carriers at high temperatures, as revealed by magnetic susceptibility, electrical resistivity and Seebeck effect. Sommerfeld coefficient 7 and Sommerfeld-Wilson ratio Rw were derived as 8.87 mJ mol-1 K-2, 1.69 for Mo3Ge2P and 9.85 mJ mol-1 K-2, 1.78 for W3Ge2P, indicating weak electron-electron correlation in the system. Analyses on thermal conductivity (x) suggest a considerable phonon contribution xL to the total one in these metallic materials. First-principles calculations demonstrate that the Mo-4d (W-5d) orbital electrons dominate the band structures and density of states near the Fermi level.

Automated summary

We report the successful synthesis of two new ternary metal-rich phosphides Mo3Ge2P and W3Ge2P, and their structural, electrical, magnetic, thermal, and electronic properties. These compounds exhibit weak magnetism and metallic conduction with electron-dominant charge carriers at high temperatures. Theoretical calculations demonstrate the dominance of Mo-4d (W-5d) orbital electrons in the band structures and density of states. Thermal conductivity analyses suggest a significant contribution of phonons to the total thermal conductivity in these metallic materials.