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  • Title: "Nanoscale zippers" in Gd5(SixGe(1-x))4: symmetry and chemical influences on the nanoscale zipping action.
    Author: Choe W, Pecharsky AO, Wörle M, Miller GJ.
    Journal: Inorg Chem; 2003 Dec 15; 42(25):8223-9. PubMed ID: 14658872.
    Abstract:
    One critical parameter influencing the structural nature of the phase transitions in magnetocaloric materials Gd5(SixGe(1-x))4 is the Si/Ge ratio (x/1-x), because transition temperatures and structures depend crucially on this value. In this study, single-crystal X-ray diffraction indicates that Si and Ge atoms are neither completely ordered nor randomly mixed among the three crystallographic sites for these elements in these structures. Ge atoms enrich the T sites linking the characteristic slabs in these structures, while Si atoms enrich the T sites within them. Decomposition of the total energy into site and bond energy terms provides a rationale for the observed distribution, which can be explained by symmetry and electronegativity arguments. For any composition in Gd5(SixGe(1-x))4, a structure map is presented that will allow for a rapid assessment of the specific structure type.
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