Morphotropy and Temperature-Driven Polymorphism in A<sub>2</sub>Th(AsO<sub>4</sub>)<sub>2</sub> (A = Li, Na, K, Rb, Cs) Series Na Yu Vladislav V. Klepov Giuseppe Modolo Dirk Bosbach Evgeny V. Suleimanov Thorsten M. Gesing Lars Robben Evgeny V. Alekseev 10.1021/ic5018246.s003 https://acs.figshare.com/articles/dataset/Morphotropy_and_Temperature_Driven_Polymorphism_in_A_sub_2_sub_Th_AsO_sub_4_sub_sub_2_sub_A_Li_Na_K_Rb_Cs_Series/2243683 A new alkaline thorium arsenate family was obtained and systematically investigated. The structures of A<sub>2</sub>Th­(AsO<sub>4</sub>)<sub>2</sub> (A = Li, Na, K, Rb, Cs) were determined from single crystal X-ray diffraction data. Li<sub>2</sub>Th­(AsO<sub>4</sub>)<sub>2</sub> and either isostructural K<sub>2</sub>Th­(AsO<sub>4</sub>)<sub>2</sub> and Rb<sub>2</sub>Th­(AsO<sub>4</sub>)<sub>2</sub> crystallize in the monoclinic crystal system. Na<sub>2</sub>Th­(AsO<sub>4</sub>)<sub>2</sub> and Cs<sub>2</sub>Th­(AsO<sub>4</sub>)<sub>2</sub> crystallize in the orthorhombic and tetragonal crystal systems, respectively. Li<sub>2</sub>Th­(AsO<sub>4</sub>)<sub>2</sub> consists of [Th­(AsO<sub>4</sub>)<sub>2</sub>]<sup>2–</sup> layers with Li atoms in the interlayer space. The rest of the compounds are based on 3D frameworks. Differences in local environments of ThO<sub>8</sub> coordination polyhedra are described in relation to the symmetry. Despite different local environments of ThO<sub>8</sub> coordination polyhedra and different structural symmetry, underlying nets of A<sub>2</sub>Th­(AsO<sub>4</sub>)<sub>2</sub> (A = Na, K, Rb, Cs) were shown to be the same. Single-crystal and powder Raman spectra were measured, and bands are assigned. DSC measurements showed phase transitions in K<sub>2</sub>Th­(AsO<sub>4</sub>)<sub>2</sub> and Rb<sub>2</sub>Th­(AsO<sub>4</sub>)<sub>2</sub>, which were studied using high-temperature powder X-ray diffraction (HT-PXRD). The data of HT-PXRD demonstrates two high-temperature polymorphic modification of K<sub>2</sub>Th­(AsO<sub>4</sub>)<sub>2</sub> and only one for the isotypic Rb<sub>2</sub>Th­(AsO<sub>4</sub>)<sub>2</sub>. The phase transitions in both K and Rb phases are reversible. 2014-10-20 00:00:00 phase transitions thorium arsenate family Li 2Th Rb 2Th powder Raman spectra 3 D frameworks DSC isostructural K 2Th ThO 8 coordination polyhedra isotypic Rb 2Th K 2Th