Structure, 119Sn solid state NMR and Mössbauer spectroscopy of RE CuSn (RE=Sc,Y,La,LuRE=Sc,Y,La,Lu)

X-ray pure samples of the stannides RE  CuSn (RE=Sc,Y,La,LuRE=Sc,Y,La,Lu) were prepared by arc-melting of the elements and subsequent annealing. The four stannides were investigated by X-ray powder and single crystal diffraction: ZrBeSi type, P63/mmcP63/mmc, a=458.3(2)a=458.3(2), c=817.3(3) pmc=817.3(3) pm, wR2=0.0746,148 F2wR2=0.0746,148 F2 values, 8 variable parameters for LaCuSn, NdPtSb type, space group P63mcP63mc, a=451.3(1)a=451.3(1), c=727.4(2) pmc=727.4(2) pm, wR2=0.0462,134 F2wR2=0.0462,134 F2 values, 10 variable parameters for YCuSn, a=446.4(2)a=446.4(2), c=709.0(2) pmc=709.0(2) pm, wR2=0.0214wR2=0.0214, BASF=0.47(2),240 F2BASF=0.47(2),240 F2 values, 12 variable parameters for LuCuSn and LiGaGe type, space group P63mcP63mc, a=438.8(1)a=438.8(1), c=683.0(2) pmc=683.0(2) pm, wR2=0.0328,220 F2wR2=0.0328,220 F2 values, 11 variable parameters for ScCuSn. The structures of the four stannides consist of layers of ordered [Cu3Sn3] hexagons. While the layers are planar in LaCuSn, a puckering effect is observed in YCuSn and LuCuSn. In ScCuSn with the smallest rare earth metal the puckering is that pronounced that a tetrahedral network occurs. The intralayer CuSn distances are similar in the four compounds (262–268 pm), but the CuSn interlayer distances decrease from 409 pm (LaCuSn) via 303 pm (YCuSn) and 289 pm (LuCuSn) to 276 pm (ScCuSn). Thus, as a function of the size of the rare earth metal, one observes a continuous transition from a two- to a three-dimensional [CuSn] network. The noncubic local symmetry at the tin site is reflected by a small nuclear electric quadrupolar splitting in the 119Sn Mössbauer spectra and a moderate chemical shift anisotropy in 119Sn solid state NMR. An inspection of all the 119Sn chemical shift anisotropies measured for RET  Sn compounds (T=Cu,Ag,AuT=Cu,Ag,Au) reveals an excellent correlation with the magnitude of the electric field gradient present at the tin site as calculated from crystal structural data by the WIEN2k program.

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