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Free keywords:
Cesium; Thallium; Cluster compounds; Crystal structure; Spin-orbit coupling; Relativistic density functional calculations
Abstract:
Cs(4)Tl(2)O was synthesized by reaction of the binary compounds CsTl and Cs(2)O at 573 K, followed by slow cooling to room temperature. According to single-crystal X-ray analysis, the title compound crystallizes in a new structure type (trigonal, space group R (3) over barm (no. 166), a = 11.986(1), c = 20.370(2) angstrom, Z = 9). It consists of isolated [Tl(6)](6-) octahedra, being regular with respect to the equality of all three main diagonals (4.546(5) angstrom), and of [Cs(12)O(3)](6+) triple octahedra extending along the c direction. The electronic structure of Cs(4)Tl(2)O was examined by relativistic density functional calculations including spin-orbit coupling and compared to the one of Rb(10)Tl(6)O(2), which exhibits a highly distorted [Tl(6)](6-) octahedra. In the latter case the closed-shell electronic structure is the result of a Jahn-Teller distortion. In contrast, the regular one in Cs(4)Tl(2)O corresponds to a closed-shell configuration, in accordance with diamagnetic properties, only if spin-orbit coupling is considered.
