Synthesis and thermal behaviour of (NH4)2Be(IO3)4 · 2H2O

Thermal dehydration of the double salts K2Be(XO4)2·2H2O (X = S, Se)

“…The comparison of the infrared and Raman spectra of the anhydrous potassium beryllium sulfate reveals that the Raman bands at 1036 and 1048 cm -1 (Fig. 4(b)) are due to ν 1 of the SO 4 2ions (the corresponding mode appears at 1043 cm -1 in the infrared spectrum, Fig. 3(b)).…”

“…The free tetrahedral ions (XO 4 n-) under perfect T d symmetry exhibit four internal vibrations: ν 1 (A 1 ), the symmetric X−O stretching mode, ν 2 (E), the symmetric XO 4 bending modes, ν 3 (F 2 ) and ν 4 (F 2 ), the asymmetric X−O stretching and XO 4 bending modes, respectively. Due to the low site symmetry C 1 of the XO 4 2ions (X = S, Se) in K 2 Be(SO 4 ) 2 ·2H 2 O and K 2 Be(SeO 4 ) 2 ·2H 2 O the ν 1 mode is activated and the degeneration of ν 2 , ν 3 and ν 4 is lifted, thus resulting in the appearance of two bands for ν 2 (2A) and three bands for ν 3 and ν 4 (3A), respectively. Due to the correlation field effects (C 2h factor group symmetry) each site group mode of A symmetry splits additionally to four components (the species A u and B u are IR and the species A g and B g are Raman active, respectively).…”

“…4(d)). The appearance of two bands corresponding to ν 1 of the XO 4 2ions in the Raman spectra of the anhydrous compounds allows us to assume that probably more than one crystallographic type of these ions exist in the lattices of K 2 Be(SO 4 ) 2 and K 2 Be(SeO 4 ) 2 .…”

“…Two sets of internal modes of the two crystallographically different XO 4 2-ions are expected to appear in the vibrational spectra. Unit-cell theoretical treatment for the translational lattice modes (all entities Be 2+ , K + (1), K + (2), XO 4 2-(1), XO 4 2-(2), H 2 O(1) and H 2 O(2) in C 1 site symmetry) and the librational lattice modes (XO 4 2-(1), XO 4 2-(2), H 2 O(1) and H 2 O(2)) yields: 21 modes of A g , A u , B g and B u symmetry and 12 modes of A g , A u , B g and B u symmetry for the translational and librational modes, respectively. The bands in the infrared regions of 1200−1060 and 1010−950 cm -1 corresponding to the ν 3 and ν 1 modes of the SO 4 2ions, respectively, appear as doublets, thus reflecting the existence of two crystallographically different [SO 4 ] -tetrahedra in the structure of K 2 Be(SO 4 ) 2 ·2H 2 O (Fig.…”

“…The present paper continues our investigations on the structures and properties of beryllium salts [1][2][3][4][5][6][7][8]. The interest in the beryllium compounds is determined by their promising physical properties.…”