Der ThCr2Si2-Typ und verwandte Strukturen bei APd2X2- Verbindungen (A = Ca, Sr, Ba; X = P, As) / The The ThCr2Si2-Type and Related Structures of APd2X2-Compounds (A — Ca, Sr, Ba; X = P, As)

Abstract

Abstract The compounds APd2X2 (A = Ca, Sr; X = P, As) have been prepared and their structures have been determined. They are isotypic and crystallize in the ThCr2Si2-type structure with the following lattice constants: CaPd2P2 a = 414.5(1) pm, c = 965.9(2) pm; CaPd2As2 a = 429.9(1) pm, c = 1010.2(2) pm; SrPd2P2 a = 424.1(1) pm, c = 972.4(2) pm; SrPd2As2 a = 438.3(1) pm, c = 1017.9(2) pm. Tetragonal symmetry was also found for BaPd2P2 (a = 425,6 pm; c = 564.7 pm) and BaPd2As2 (a = 434.6 pm; c = 575.8 pm ), but these materials crystallize in a CeMg2Si2-type structure, whereas the lattice of some selected single crystals of BaPd2As2 have tetragonal symmetry (a = 448.7 pm; c = 2063.5 pm) and show structural elements of CaBe2Ge2 - like those of the CeMg2Si2-type structure.