Crystallization of MoGe2 and WGe2 at high pressure and some properties of these phases

Crystal and Electronic Structures of MoSi2-Type CrGe2 Synthesized under High Pressure

“…36−38 WGe 2 also crystallizes in two polymorphs, α phase (PbCl 2 type) and β phase (MoSi 2 type), but both are formed only under high pressure. 38 The fact that MoSi 2 -type β-MoGe 2 and β-WGe 2 phases are only thermodynamically stable phases at gigapascal pressures is consistent with our highpressure synthesis of MoSi 2 -type CrGe 2 . In general, the axial ratio c/a of MoSi 2 -type AB 2 compounds, which is in the range of 2.2 to 2.9, increases when the B atom is larger than the A atom.…”

“…The c / a of MoSi 2 , which is a representative compound having a MoSi 2 -type structure, is about 2.45. The c / a of MoSi 2 -type digermanides synthesized under high pressure is 2.478 for CrGe 2 , 2.474 for β-MoGe 2 , and 2.473 for β-WGe 2 . The c / a of these digermanides is larger than that of MoSi 2 , reflecting the difference in atomic size between Si and Ge.…”

“…The c/a of MoSi 2type digermanides synthesized under high pressure is 2.478 for CrGe 2 , 2.474 for β-MoGe 2 , 38 and 2.473 for β-WGe 2 . 38 The c/a of these digermanides is larger than that of MoSi 2 , reflecting the difference in atomic size between Si and Ge. Takizawa and coauthors proposed that the amount of Ge increases from NCL-phase TMGe 2−x to stoichiometric TMGe 2 and that TM digermanides crystallize in the MoSi 2 -type, CrSi 2 -type, or TiSi 2 -type structure on the basis of high-pressure synthesis experiments.…”

“…In germanides of Mo and W, which are homologous elements of Cr, only MoGe 2 and WGe 2 have been reported as digermanides next to the novel CrGe 2 . MoGe 2 has two polymorphs, the α phase (PbCl 2 type) and β phase (MoSi 2 type), whereby the β phase was obtained as a mixture with the α phase under ambient pressure and as a single phase under high pressure. − WGe 2 also crystallizes in two polymorphs, α phase (PbCl 2 type) and β phase (MoSi 2 type), but both are formed only under high pressure . The fact that MoSi 2 -type β-MoGe 2 and β-WGe 2 phases are only thermodynamically stable phases at gigapascal pressures is consistent with our high-pressure synthesis of MoSi 2 -type CrGe 2 .…”

Anomalous small angle x-ray scattering studies of amorphous metal-germanium alloys

“…They claim that W2Ge3 is isomorphous with Mo2Ge3, but Mo2Ge3 is actually Mo_3Ge23. Subsequent authors (Popova & Fomicheva, 1978;and Agoshkov, Gorbatenkov, Popova, & Fomicheva, 1981) returned to the claim that there are no compounds in the W-Ge system at atmospheric pressure. These authors were able to obtain W-Ge compounds at high pressures (77 kbars), but none of these phases was WzGe3.…”