ChemInform Abstract: Structure Determination of a Low Temperature Phase of Calcium and Strontium Amide by Means of Neutron Powder Diffraction on Ca(ND2)2 and Sr(ND2)2.
Abstract
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ChemInform Abstract
Ca(NH2)2 and Sr(NH2)2 are ionic compounds crystallizing in a tetragonally distorted anatase type structure at room temperature. A temp.-dependent neutron diffraction study at temperatures below 90 K reveals the existence of a hitherto unknown low-temp (LT) phase. The LT-phases are isotypic and crystallize in the monoclinic space group P21/c with Z = 4. The structure is closely related to that of the high-temp. phase, but ordering of the amide ions occurs due to freezing of a lattice mode that is dominated by the librational motion of the amide ions in the {100} planes of the high-temp. phase.
