Crystal structure, specific heat, and ¹¹⁹Sn Mössbauer spectroscopy of CeRu₄Sn₆: a ternary stannide with condensed, distorted RuSn₆ octahedra

Abstract

CeRu₄Sn₆ was prepared from the elements by a reaction in an arc-melting furnace and subsequent annealing at 1123 K. It crystallizes with the tetragonal YRu₄Sn₆ type structure of space group/4̅2m:a=688.1(1), c=975.2(2) pm, V=0.4617(1) nm³, wR2=0.0472, 554F² values, and 19 variables. The cerium atoms in CeRu₄Sn₆ have coordination number 16 formed by 12 tin and 4 ruthenium atoms. These polyhedra are arranged in a tetragonal body-centered packing and are linked by common Sn1 atoms. The strongest bonding interactions are between ruthenium and tin atoms. The ruthenium atoms have 6 tin neighbors at distances from 256.9 to 276.8 pm in the form of a strongly distorted octahedron. Four of such octahedra are condensed via common edges and faces forming [Ru₄Sn₆] units. These groups are packed in a tetragonal body-centered arrangement. The cerium atoms occupy the space between the [Ru₄Sn₆] units. The [Ru₄Sn₆] substructure of CeRu₄Sn₆is discussed in comparison with the structures of Ru₂Sn₃, LaRuSn₃, and Ru₃Sn₁₅O₁₄ which also contain condensed RuSn₆octahedra or trigonal prisms as characteristic structural motifs. Despite the two different tin sites the ¹¹⁹Sn Mössbauer spectroscopic measurements show only one signal at δ=1.99 mm/s subjected to quadrupole splitting. Heat capacity measurements indicate that CeRu₄Sn₆ behaves like a heavy-fermion compound.