Vibrational spectra of and phase transitions in caesium hydrogen sulphate

Abstract

The Raman and infrared spectra of the superionic protonic conductor CsHS04(CsDS04) were investigated in the 18450 K range. Polarized single crystal Raman and infrared reflection spectra were also studied at room temperature. An assignment of bands due to internal and external vibrations is given in terms of symmetry species and approximate type of motion. The spectroscopic results, in particular the behaviour of the Raman bands as a function of temperature, are used to discuss the crystalline structures of various phases, hydrogen bonding, the type and degree of structural disorder, phase transitions and conductivity.

High-resolution neutron powder diffraction studies of the structure of CsDSO4

“…The structural results indicate no possiblity of the Cs ÷ diffusion as reported elsewhere (Pham-Thi, Colomban, Novak & Blinc, 1987). Haynovskiy, Pavlyuhin & Hayretdinov (1985) reported that in the low-temperature phase the conductivity of CsHSO4 is two orders of magnitude higher than that of CsDSO4, whilst in the superionic phase their conductivities are approximately equal.…”

“…Haynovskiy, Pavlyuhin & Hayretdinov (1985) reported that in the low-temperature phase the conductivity of CsHSO4 is two orders of magnitude higher than that of CsDSO4, whilst in the superionic phase their conductivities are approximately equal. From this arose tlte assumption that the diffusion of Cs ÷ contributes to the conductivity (Pham-Thi, Colomban, Novak & Blinc, 1987). However as noted above the room-temperature structure of CsHSO4 differs from that of CsDSO4 and so the large difference in conductivity in the lowtemperature phases of protonated and deuterated samples cannot be solely assigned to an isotopic effect as previously stated (Haynovskiy, Pavlyuhin & Hayretdinov, 1985).…”

“…From previous work, however, two models for the O and D atomic positions have been proposed -16(h) and 8(e) sites (Merinov, Baranov, Shuvalov & Maksimov, 1987) and 32(/) and 16(]) sites (Jirak, Dlouha & Vratislav, 1987) for the respective atoms. Distinction between the two models is necessary as is consideration of the optical spectroscopy data (Pham-Thi, Colomban, Novak & Blinc, 1985& Blinc, , 1987Dmitriev, Loshkarev, Rabkin, Shuvalov & Yuzyuk, 1986) which indicates rotation of SO4--H groups in the superionic phase, incompatible with either of the previously proposed structural models. In order to reduce the number of variables in the high-temperature refinement, sample characteristics were fixed to those obtained from the roomtemperature data wherever possible.…”

“…Each tetrahedron is seen to adopt one of four orientations as shown in Table 6. One tetrahedron may be transformed to another by a rotation of OI--S----OI' = 107.2 (2) OI--S---O2 = 108.9 (3) OI--S---492' = 1125 (3) 01'--S---02 = 112-5 (3) 01"--S--02" = 108.9 (2) 02--S--02' = 107.1 (4) & Blinc, 1985& Blinc, , 1987. One of the possible orientations of the SO4 tetrahedra, along with the associated hydrogen-bonding scheme, is shown projected on the ab crystal plane in Fig.…”

Crystal Structure and Characterization of CsH5(AsO4)2: A New Cesium Pentahydrogen Arsenate, and Comparison with CsH5(PO4)2 and RbH5(AsO4)2

“…We distinguish the (AsO ) by the intense Raman band at about 767 cm\, and by the shoulder and the intense infrared bands near 760 and 782 cm\, respectively. Yet the vibration is not degenerated ( (a )), which is why this weak splitting is not to the crystal "eld, but to the coexistence of two H AsO\ and H AsO constituting the dimer (H AsO HAsO H )\ (26,27). By analogy with M H(SO ) (M"Na, K, Rb, and NH ) (28,29), the band with high frequency is attributed to the H As(2)O\ group ( (H As(2)O\ )), whereas the one with low frequency is correlated to the H As(1)O4 group ( (H As(1)O )).…”