Synthesis, crystal and electronic structures and magnetic properties of Li2SnMo3O8: A novel reduced molybdenum oxide containing Mo3O13 cluster units

Abstract Powder samples and single crystals of the quaternary oxide Li 2 SnMo 3 O 8 were obtained by solid state reaction. The structure was determined by single-crystal X-ray diffraction. Li 2 SnMo 3 O 8 crystallizes in the hexagonal space group P 6 3 mc with unit-cell parameters a =5.7720 (2) A, c =10.3941 (3) A and Z =2. Full-matrix least-squares refinement on F 2 using 930 independent reflections for 31 refinable parameters results in R 1 =0.0354 and w R 2 =0.0643. The crystal structure consists of distorted hexagonal-close-packed oxygen layers with stacking sequence abac along [0 0 1] and that are held together by alternating lithium-tin and molybdenum layers. The Li + and Sn 4+ ions occupy, respectively, tetrahedral and octahedral sites in the ratio 2:1. The Mo atoms occupy octahedral sites and form strongly bonded triangular clusters involving three MoO 6 octahedra that are each shared along two edges, constituting a Mo 3 O 13 unit. Magnetic susceptibility measurements are in agreement with a spin-pairing of the eight d electrons per Mo 3 cluster. The electronic structure of Li 2 SnMo 3 O 8 is analyzed using periodic density functional calculations.