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http://repositoriodigital.ipn.mx/handle/123456789/10698| Título : | Low temperaturestructuraltransformationin T[Ni(CN)4]·xpyz with x=1,2; T=Mn,Co,Ni,Zn,Cd;pyz=pyrazine |
| Palabras clave : | Crystal chemistry Low Temperature structure Leyered compounds Pillared compounds |
| Fecha de publicación : | 16-ene-2013 |
| Editorial : | ELSEVIER |
| Descripción : | The materials under study are pillared solids T[Ni(CN)4]·xpyz with one and two(x=1,2) pyrazine (pyz) molecules and where T= Mn, Co, Ni, Zn, Cd. Stimulated by their structural features and potential role as prototype of porous solids for hydrogen storage, the structural stability under cryogenic conditions for this series of pillared solids was studied. At lowtemperature, in the 100–200 K range, the occurrence of a reversible structural transformation was found. For T= Mn, Co, Zn, Cd, with x=2,the structural transformation was observed to occur around 185 K, and the low temperature phase crystallizes with a monoclinic unit cell (spacegroup Pc). This structure change results from certain charge redistribution on cooling within the involved ligands. For T=Ni with x=1, both the low and high temperature phases crystallize with unit cells of tetragonal symmetry, within the same space group but with a different unit cell volume. In this case the structure change is observed around 120 K. Above that temperature the rotational states for the pyrazine molecule are thermally excited and all the pyrazine molecules in the structure become equivalent. Under this condition the material structure is described using a smaller structural unit. The structural study usingX-ray powder diffraction data was complemented with calorimetric and Raman spectroscopy measurements. For the low temperature phases the crystal structures were solved from Patterson methods and then refined using the Rietveld method. |
| URI : | http://www.repositoriodigital.ipn.mx/handle/123456789/10698 |
| Otros identificadores : | J SOLID STATE CHEM 183 (2010) 105-113 0022-4596 http://hdl.handle.net/123456789/181 |
| Aparece en las colecciones: | Doctorado |
Ficheros en este ítem:
| Fichero | Descripción | Tamaño | Formato | |
|---|---|---|---|---|
| 10 JSSC Lemus-Santana Low T transformation.pdf | 697.64 kB | Adobe PDF | Visualizar/Abrir |
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