Simultaneous presence of (Si3O10)8- and (Si2O7)6- groups in new synthetic mixed sorosilicates: BaY4(Si2O7)(Si3O10) and isotypic compounds, studied by single-crystal X-ray diffraction, Raman spectroscopy and DFT calculations

Three new, isotypic silicate compounds, BaY4(Si2O7)(Si3O10), SrYb4(Si2O7)(Si3O10) and SrSq(Si2O7)(Si3O10), were synthesized using high-temperature flux growth techniques, and their crystal structures were solved from single-crystal X-ray intensity data: monoclinic, P2i/m, with a= 5.532(1)/5A69(1)/5.278(1), b= 19.734(4)/19.447 (4)/19.221(4), c= 6.868(1)/6.785(1)/6.562(1) A, g= 106.53(3)/106.20(3)/106.50(3), V= 718.8(2)/693.0(2)/638.3 (2)P, R(F)= 0.0225/0.0204/0.0270, respectively. The topology of the novel structure type contains isolated horseshoe-shaped Si3O10 groups (Si-Si-Si= 93.15-95.98 1 Si2O7 groups (Si-Obridge-Si=180, symmetryrestricted) and edge-sharing M(1)06 and M(2)06 octahedra. Single-crystal Raman spectra of the title compounds were measured and compared with Raman spectroscopic data of chemically and topologically related disilicates and trisilicates, including BaY2(Si3O10) and SrY2(Si3O10). The band assignments are supported by additional theoretical calculation of Raman vibrations by DFT methods. (C) 2013 Elsevier Inc. All rights reserved.