Crystal and electronic structure, thermochemical and photophysical properties of europium-silver sulfate monohydrate AgEu(SO4)(2)center dot H2O

In order to synthesize single crystals of europium-silver double sulfate monohydrate, a hydrothermal reaction route was used. It was found that the crystallization cannot be performed under standard conditions. The compound AgEu(SO4)(2)center dot H2O crystallizes in the trigonal crystal system, space group P3(2)21 (a = 6.917(1), c = 12.996(2) angstrom, V = 538.53(17) angstrom(3)). The structure consists of triple-capped trigonal prisms [EuO9], in which one oxygen atom belongs to crystalline water, silver octahedra [AgO6], and sulfate tetrahedra [SO4]. The hydrogen bonds in the system additionally stabilize the structure. The electronic band structure wasstudied by density functional theory calculations which show that AgEu(SO4)(2)center dot H2O is an indirect band gap dielectric. Temperature dependent photoluminescence spectroscopy shows emission bands of transitions from the D-5(0) state to the spin-orbit components of the F-7(J) multiplet (J = 0-6).The ultranarrow transition D-5(0) - F-7(0) shows a red shift with respect to other europium-containing water-free sulfates that is ascribed to the presence of OH group in the crystal structure in the close vicinity of the Eu3+ ion. An effect of abnormal sensitivity of the Omega(4) intensity factor to minor distortions of the local environment is detected for the observed low local symmetry of C-2.