Preparation, properties and crystal structures of the thorium chromium borides ThCrB4 and ThCr2B6; structure refinements of CeCr2B6, ThB4 and ThB6

Article abstract of DOI:10.1016/0925-8388(95)01993-6

The new polyborides ThCrB₄ and ThCr₂B₆ were prepared by arc melting of the elemental components, and their crystal structures were determined from single-crystal X-ray data. ThCrB₄ has a YCrB₄-type structure: Pbam, a = 605.8(1) pm, b = 1171.2(2) pm, c = 364.0(1) pm, R = 0.024 for 714 structure factors and 26 variable parameters. ThCr₂B₆ is isotypic with CeCr₂B₆: Immm, a = 315.8(1) pm, b = 659.1(1) pm, c = 836.4(2) pm, R = 0.030 (415 F values, 14 variables). The structures of the borides CeCr₂B₆, ThB₄ and ThB₆ were refined from single-crystal X-ray data. The B-B bonds between the B₆ octahedra of ThB₄ and ThB₆ are considerably shorter than those within the octahedra. ThCrB₄, ThCr₂B₆ and CeCr₂B₆ are metallic conductors and Pauli paramagnetic.