Structural Phase Transitions and Vibrational Study of CsH(SO4)0.76(SeO4)0.24

Autor: T. Jouini, Abdelaziz Daoud, T. Mhiri, Mohamed Gargouri
Rok vydání: 1997
Předmět:
Zdroj: physica status solidi (b). 200:3-11
ISSN: 1521-3951
0370-1972
Popis: CSH(SO 4 ) 0.76 (SeO 4 ) 0.24 , M m = 241.2, single crystals were grown and appear to be isomorphous with CsHSeO 4 . The space group is P2 1 /a, the lattice constants are: a = 7.8340(10) A, b = 8.2147(6) A, c = 7.4440(10) A, β = 110.910(10)°, V = 447.50(9) A 3 , Z = 4, D x = 3.582 Mg m -3 , λ (MoK α ) = 0.71069 A, μ(MoK α ) = 10.269 mm -1 . F(000) = 818, T = 293(2) K (room temperature phase), R = 0.023 and wR = 0.0563 for 883 observed reflections. The hydrogen sulphate or hydrogen selenate groups are connected by hydrogen bonds. The separated chains of asymmetric hydrogen bonds run parallel to the c-axis. The O-H...O distance utilized in the hydrogen bonding is 2.608 A which is 2.603 A for CsHSeO 4 . Mixed cesium hydrogen sulphate selenate CsH(SO 4 ) 0.76 (SeO 4 ) 0.24 undergoes two phase transitions at T = 333 and 408 K. The values of the enthalpies are 2.02 and 4.37 kJ/mol, respectively.
Databáze: OpenAIRE
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