Structure of the intercalate Na1.5WO2Cl2 by powder neutron diffraction

Abstract

The crystal structure of the intercalation compound Na_1.5WO₂Cl₂ has been refined using powder neutron diffraction. Refinement was carried out in the tetragonal space group, I4/mmm, with a= 3.8809(4)Å, c= 15.102(2)Å, V= 227.46(7)ų, Z= 2. The final R factors are R_wp= 4.84%, R_ex= 2.43%, χ²= 4.00 for 20 basic variables with 2699 observations corresponding to 54 reflections. The structure, which is closely related to that of the unintercalated host WO₂Cl₂, consists of layers of tungsten oxide sandwiched between chloride ions to form trilayer blocks of general formula [ClWO₂Cl]_n. These blocks stack in the c direction to generate the three-dimensional structure, which is stabilised by van der Waals interactions. Na⁺ ions are located outside the van der Waals gap within the trilayer blocks and are coordinated to four chlorine and four oxygen atoms in a square antiprismatic coordination.