Crystal structure of the high-pressure modification of NdTaO4

The crystal structure of the metastable NdTaO4 high-pressure modification ( HPM) has been studied by X-ray powder diffraction.. It was found that the c rystal structure of HPM NdTaO4 belongs to the monoclinic LaTaO4-type struct ure (space group P2(1)/c, a=7.5920(7) Angstrom, b=5.4673(5) Angstrom, c = 7 .7022(7) Angstrom, beta = 100.032(6)degrees Z=4). The difference in structu re between LnTaO(4) with Ln=Nd-Lu (fergusonite-type structure) and that wit h Ln=La-Pr (monoclinic LaTaO4-type structure) is most Likely due to the dif ference in size of the rare-earth cations. (C) 2000 Elsevier Science S.A. A ll rights reserved.