An Extension of Pnictide Oxide Chemistry - Salt Flux Synthesis and Structure of La5Cu4As4O4Cl2

作者：Eul Matthias; Johrendt Dirk; Poettgen Rainer

来源：Zeitschrift fur Naturforschung Section B-A Journal of Chemical Sciences, 2009, 64(11-12): 1353-1359.

DOI：10.1515/znb-2009-11-1215

• Arsenide Oxide
• Crystal Chemistry
• Electronic Structure

La5Cu4As4O4Cl2 was prepared from a cold-pressed pellet of lanthanum filings, ground arsenic, Cu2O and LaOCl in the ideal 3 : 4: 2: 2 ratio. The pellet was annealed in an evacuated silica tube at 1473 K for two days and then cooled down to room temperature. LaOCl was always observed as a by-product. La5Cu4As4O4Cl2 crystallizes with a new structure type: I4/mmm, a = 413.46(7), c = 4144(1) pm, wR2 = 0.0763, 328 F-2 values, 26 parameters. The new quaternary arsenide oxide La3Cu4As4O2 with La3CuP4O2-type structure (I4/mmm) was obtained in polycrystalline form: a = 413.0(1), c = 2748.6(1) pm. The structure of La5Cu4As4O4Cl2 is an intergrowth of structural slabs of LaOCl (PbFCl type), ZrCuSiAs- and La3Cu4P4O2-related slabs. The copper atoms have tetrahedral arsenic coordination, and all oxygen atoms fill lanthanum tetrahedra. In the LaOCl slab we observe a van der Waals gap built up by the chloride anions. Half of the arsenic atoms within the La3Cu4P4O2-related slab form As-2(4-) dumb-bells at an As-As distance of 249 pm. Electronic band structure calculations reveal La5Cu4As4O4Cl2 as a strongly anisotropic hybride material, composed of covalently bonded metallic CuAs4/4 layers, sandwiched between ionic insulating oxide and chloride blocks.

• 出版日期2009-12