Bonhomme, F.

Fischer, P.

Gingl, F.

Yvon, K.

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Tetracalcium Trimagnesium Tetradekahydride,Ca4Mg3H14:The First Ternary Alkaline Earth Hydride*By F. Gingl, F. Bonhomme, K. YvonLaboratoire de Cristallographie, Université de Genève, 24, Quai E. Ansermet,CH-1211 Genève 4, Switzerlandand P. FischerLabor für Neutronenstreuung, ETH Zürich, CH-5232 Villigen PSI, SwitzerlandThe title compound and its deuteride, Ca4Mg3D14, were prepared fromCaMg alloy at 410(10)°C (deuteride: 458(8)°C) under 53(3) bar hydrogen(95(5) bar deuterium) pressure, and characterized by X-ray and neutronpowder diffraction. The compound crystallizes with a new hexagonalDeuterium coordination polyhedra around the metal atoms in hexagonal Ca4Mg3D14,projected along [0001]. (a) tricapped trigonal prisms around Cal (thin lines) and Ca2(thick lines); (b) pentagonal bipyramids around Mg. Cal in z = 0.27, Ca2 in z = 1/2,Mg in z = 0, Dl in z = 0.27, D2 in z = 1/2, D3 and D4 in z = 0.* Presented at the International Symposium on Metal —Hydrogen Systems, Funda-mentals and Applications, Uppsala, Sweden, June 8—12, 1992.339F. Gingl, F. Bonhomme, K. Yvon and P. Fischerstructure type (space group P62m (189); lattice parameters at 20 °C:a = 6.3056(2) A, c = 6.8820(2) A (hydride), a = 6.2902(2) A, c =6.8540(3) Â (deuteride), Z = 1) that contains an ordered array of foursymmetry independent deuterium atoms having respectively tetrahedral(Dl: [3Ca, Mg], D2: [4Ca]), trigonal bipyramidal (D3: [2Ca, 3Mg]) andtriangular (D4: [3Mg]) metal coordinations. The metal—deuterium bonddistances range from 1.85 to 2.44 A (Mg-D) and from 2.29 to 2.48 Â(Ca-D).340

Tetracalcium Trimagnesium Tetradekahydride, Ca4Mg3H14: The First Ternary Alkaline Earth Hydride*

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