A temperature-dependent, single crystal x-ray diffraction study of the giant magnetocaloric material, Gd5(Si2Ge2), across its Curie temperature (276 K) reveals that the simultaneous orthorhombic to monoclinic transition occurs by a shear mechanism in which the (Si, Ge)-(Si,Ge) dimers that are richer in Ge increase their distances by 0.859(3) A and lead to twinning. The structural transition changes the electronic structure, and provides an atomic-level model for the change in magnetic behavior with temperature in the Gd5(SixGe1-x)(4).

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Composition, crystal structure, and stability of the thermoelectric material, known in the literature as "Zn 4 Sb 3 ", has been characterized using low-and room-temperature single-crystal X-ray diffraction techniques, as well as in situ room-and high-temperature powder X-ray diffraction methods. We have found that the Zn 4 Sb 3 phase does not exist below 767 K (the β−γ transition temperature); it is the Zn 6-δ Sb 5 phase that is erroneously assigned the Zn 4 Sb 3 composition and is considered to be a promising thermoelectric material. The structure of Zn 6-δ Sb 5 is similar to that of "Zn 4 Sb 3 " but no Zn/Sb mixture is observed on any Sb site. Instead, a significant deficiency on the Zn site is discovered. There are two, not one, as previously reported, Zn 6-δ Sb 5 polymorphs below room temperature. In dynamic vacuum and at elevated temperatures the Zn 6-δ Sb 5 phase becomes zinc poorer due to zinc sublimation and eventually decomposes into ZnSb and Zn before reaching its melting temperature of 841 K. The binary Zn 1-δ Sb compound also loses zinc in dynamic vacuum and at high temperatures and decomposes into Sb and Zn. The structure of Zn 1-δ Sb (CdSb-type) is analyzed using powder X-ray diffraction techniques. Disciplines