Rune Liminga

Hydrogen bond studies. 54. A neutron diffraction study of the ferroelectric lithium trihydrogen selenite, LiH3(SeO3)2

Abstract The crystal structure of the ferroelectric LiH 3 (SeO 3 ) 2 has been studied using three-dimensional neutron diffraction data. The position of the heavy atoms are in agreement with earlier investigations, whereas the hydrogen bond network differs considerably. The present study reveals three almost linear OH · O hydrogen bonds of length 2.518, 2.552, and 2.646 A with OH · O angles 176.6, 173.3, and 172.3°, respectively. The shortest bond has an OH distance of 1.14 A, which is longer than expected. The lithium ion is surrounded by six oxygen atoms forming an octahedron with LiO distances in the range 2.13–2.22 A.

Hydrogen bond studies 78. A neutron diffraction study of lithium formate monohydrate, LiHCOO·H2O

The crystal structure of lithium formate monohydrate has been determined from three-dimensional neuiron diffraction data. Two different hydrogen bonds occur in the crystal: an O(W)-H … O(W), 2.896(2) A bond linking together the water molecules to produce infinite chains, and an O(W)-H … O, 2.714(2) A bond connecting the water chains to the formate ions. The O-H … O angles are 166.6(3)° and 173.6(3)°, respectively. The water molecules have O-H distances 0.965(4) and 0.976(3) A, and an H-O-H angle of 107.8(3)°.

88. An X-ray diffraction study of the paraelectric phase of cesium trihydrogen selenite, CsH3(SeO3)2

The crystal structure of CsH3(SeO3)2 has been determined from three-dimensional single crystal x-ray diffractometer data obtained at room temperature. Two formula units crystallize in a triclinic unit cell of dimensions a = 9.3474(5), b = 6.5398(4), c = 5.8498(3) A, α = 91.443(6), β = 105.336(6), γ = 91.629(6) degrees. The space group is P1 The structure is built up of two types of O-Se-O-H…O-Se-O chains with disordered hydrogen positions. The hydrogen atoms were located from difference Fourier maps and were included in the last cycles of refinement. The final agreement factor was R(F) = 0.017.

Hydrogen bond studies: 67. The crystal structure of rubidium trihydrogen selenite, RbH3(SeO3)2

Abstract The crystal structure of RbH 3 (SeO 3 ) 2 has been determined from three-dimensional single crystal X-ray diffractometer data obtained at room temperature. Four formula units crystallize in an orthorhombic unit cell of dimensions: a = 5.9192(2), b = 17.9506(5), and c = 6.2519(3) A. The space group is P 2 1 2 1 2 1 . The structure consists of two types of chains at a right angle. One chain is built up of H 2 SeO 3 molecules linked by 2.594(8)-A hydrogen bonds and the other of HSeO 3 − ions linked by 2.571(12)-A hydrogen bonds. These two types of chains are cross-linked by a third hydrogen bond of length 2.521(7) A. The rubidium ion is surrounded by eight oxygen atoms forming a distorted cube. The Rb + O distances are in the range 2.94–3.19 A.

Hydrogen bond studies

The crystal structure of RbH3(SeO3)2 has been investigated from three-dimensional single crystal neutron diffraction data obtained at room temperature. The asymmetric unit consists of an Rb+ ion, an HSeO3- ion and an H2SeO3 molecule.The SeO3-groups are connected to form a three-dimensional network via three almost linear O-H … O hydrogen bonds of lengths 2.599(2), 2.570(3) and 2.512(2) A. No disorder has been observed in the structure.

Molecular model of radiation damage in Cs2S2O6 crystals at room temperature

Abstract During the course of a crystal structure determination of caesium dithionate it was noticed that radiation damage occurred under the influence of the X-rays used in the diffraction experiments. In the present paper a molecular model for the damage centres is proposed on the basis of ESR studies. One centre showing hyperfine structure with 133 Cs is assigned to the · SO − 3 ..... C + 3 radical ion. Another centre is tentatively ascribed to the ·SO − 2 radical ion.

Phase Transitions in CsH3(SeO3)2 and CsD3(SeO3)2

Three phase transitions have been observed in CsD3(SeO3)2 using differential scanning calorimetry combined with measurements of the temperature dependence of the dielectric constant, lattice constants, and superlattice-reflection intensities. It is shown that a transition at -65°C reported for the first time corresponds to the antiferroelectric -128°C transition in CsH3(SeO3)2. Two additional transitions in the deuterated compound were observed in the room-temperature range, both accompanied by pronounced thermal hysteresis. One of these phases may appear in a monoclinic modification, in contrast to the triclinic antiferroelectric and paraelectric phases.