Tetragonal-antiprismatic coordination of transition metals in intermetallic compounds: ω1-Mn6Ga29 and its structuralrelationships

摘要

The new phase ω_1-Mn_6Ga_(29) was synthesised in single-crystal form from the elements applying the high-temperature centrifugation-aided filtration technique. The crystal structure was determined using diffraction data collected from a twinned specimen: a new prototype, space group P1?; a=6.3114(2) ?…, b=9.9557(3) ?…, c=18.920(1) ?…, α=90.473(1)°, β=90.847(1)°, γ=90.396(1)°; R1=0.047, wR2=0.117 for 317 variable parameters and 7346 observed reflections; twinning matrix 0 0 -13, 0 -1 0, -3 0 0; twin domains ratio 0.830(3):0.170. All manganese atoms in the crystal structure of ω_1-Mn_6Ga_(29) are coordinated exclusively by Ga forming distorted tetragonal antiprisms. The monocapped [MnGa_(8+1)] antiprisms condense into pairs by sharing their pseudo-quadratic faces and are interconnected via common apexes and edges to form a 3D framework. The relationship between the crystal structures of ω_1-Mn_6Ga_(29) and CuAl_2, α-, β-CoSn_3, PtSn_4, Ti_4MnBi _2, PdGa_5, Rh_3Ga_(16), Rh _4Ga_(21), Al_7FeCu_2, Co _2Al_9, and RhBi_4 is discussed.