Hydrogen-Bonding and Phase Transitions in Proton-Conducting Solid Acids

1998 ◽  
Vol 547 ◽  
Author(s):  
Sossina M. Haile
Keyword(s):  
High Temperature ◽  
Hydrogen Bonds ◽  
Solid Acid ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Temperature Structure ◽  
System A ◽  
Superprotonic Phase ◽  
Oxygen Site ◽  
Oxygen Atoms

AbstractFrom an investigation of the structures and electrical properties of compounds in the CsHSO4 - CsH2PO4 system, a simple model is presented for predicting whether or not a solid acid will undergo a structural transition to a disordered, superprotonic phase. Such a transition was measured in ß-Cs3(HSO4)2(H2-x(SxP1-x)O4), α-Cs3(HSO4)2(H2PO4) and Cs2(HSO4)(H2PO4), but not CsH2PO4. It is proposed that entropy drives any solid acid to a high-temperature structure in which the oxygen atoms participate equally in forming hydrogen bonds. If the H:XO4 ratio is not precisely 2:1, such chemical equivalence of oxygen atoms can only be achieved if the structure transforms to a state in which proton occupancies at hydrogen bonds are less than one and/or oxygen site occupancies are less than one. This disorder simultaneously leads to fast proton transport in the high-temperature phase, and thus superprotonic conductivity.

Superprotonic high temperature phase and refinement of the low temperature structure of CsHSeO4

2001 ◽  
Vol 216 (3) ◽  
Author(s):  
M. A. Zakharov ◽  
Sergej I. Troyanov ◽  
Erhard Kemnitz
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Low Temperature ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Temperature Structure ◽  
Superprotonic Phase

AbstractThe crystal structure of the high temperature superprotonic phase of CsHSeO

Disorder of (NH4)3H(SO4)2 in the high-temperature phase I

2011 ◽  
Vol 67 (2) ◽  
pp. 116-121 ◽  
Author(s):  
Yoo Jung Sohn ◽  
Karine M. Sparta ◽  
Martin Meven ◽  
Gernot Heger
Keyword(s):  
High Temperature ◽  
Hydrogen Bonds ◽  
Phase I ◽  
Careful Consideration ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Atom Model ◽  
Disordered Crystal ◽  
Proton Migration ◽  
Atom Position

The highly disordered crystal structure of triammonium hydrogen disulfate, (NH4)3H(SO4)2, in the high-temperature phase I was studied using single-crystal neutron diffraction. It is known that the O atom involved in hydrogen bonding between neighbouring SO4 tetrahedra is disordered and takes a split-atom position, building a two-dimensional hydrogen-bond network in the (001) plane. The H atoms in these SO4–H—SO4 hydrogen bonds are disordered and hence refined with a split-atom model. Moreover, from the much larger anisotropic mean-square displacements of ammonium protons the NH_4^+ groups were refined with a reasonable split-atom model, and their motional behaviour was also analysed by rigid-body treatment. Finally, careful consideration was given to show possible supplementary proton migration between the ammonium protons and those of the hydrogen bonds in this high-temperature phase.

Crystal Structure of Bis(triethylammonium)closo-decahydrodecaborate, [(C2H5)3NH]2[B10H10]

2000 ◽  
Vol 55 (6) ◽  
pp. 499-503 ◽  
Author(s):  
Kathrin Hofmann ◽  
Barbara Albert
Keyword(s):  
Crystal Structure ◽  
High Temperature ◽  
Powder Diffraction ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
X Ray ◽  
Crystal System ◽  
System A ◽  
Tetragonal Crystal ◽  
Tetragonal Crystal System

The crystal structure of bis(triethylammonium)closo-decahydrodecaborate [bis(triethylammonium) decaboranate(10)], [(C2H5)3NH]2[B10H10], was determined and refined (space group Pmmn, no. 59, a = 989.7, b = 1333.7, c = 903.7 pm). The compound is a versatile starting material for many substances containing the [BioHio]2- entity and its derivatives. The closo-[B10H10]2- cluster is a bicapped square antiprism which is only slightly distorted. Its deviation from D4d symmetry is smaller than that of the B10 cages in every other compound containing this entity that have been structurally characterised. The presence of additional (N )H ---B3 interactions in form of multiple-centre bonds between the cations and the anions, which were postulated earlier and which should influence the cage symmetry, could not be confirmed. At 55 °C, the transition into a high temperature phase was investigated by X-ray powder diffraction. The high temperature phase crystallises in the tetragonal crystal system (a = 946.9, c = 1351.0 pm).

Reversible high-temperature phase transition of a manganese(II) formate framework with imidazolium cations

2013 ◽  
Vol 69 (6) ◽  
pp. 616-619 ◽  
Author(s):  
Bi-Qin Wang ◽  
Hai-Biao Yan ◽  
Zheng-Qing Huang ◽  
Zhi Zhang
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Low Temperature ◽  
Variable Temperature ◽  
Structural Phase ◽  
High Temperature Phase ◽  
Mirror Plane ◽  
Temperature Phase ◽  
Temperature Structure ◽  
Imidazolium Cations

A new metal–formate framework, poly[1H-imidazol-3-ium [tri-μ2-formato-manganese(II)]], {(C3H5N2)[Mn(HCOO)3]}n, was synthesized and its structural phase transition was studied by thermal analysis and variable-temperature X-ray diffraction analysis. The transition temperature is around 435 K. The high-temperature phase is tetragonal and the low-temperature phase is monoclinic, with a β angle close to 90°. The relationship of the unit cells between the two phases can be described as:aHT= 0.5aLT+ 0.5bLT;bHT= −0.5aLT+ 0.5bLT;cHT = 0.5cLT. In the high-temperature phase, both the framework and the guest 1H-imidazol-3-ium (HIm) cations are disordered; the HIm cations are located about 2mmsites and were modelled as fourfold disordered. The Mn and a formate C atom are located on fourfold rotary inversion axes, while another formate C atom is on a mirror plane. The low-temperature structure is ordered and consists of two crystallographically independent HIm cations and two crystallographically independent Mn2+ions. The phase transition is attributable to the order–disorder transition of the HIm cations.

Pyramidal Slip in β Boron

1991 ◽  
Vol 49 ◽  
pp. 944-945
Author(s):  
D.M. Vanderwalker
Keyword(s):  
High Temperature ◽  
High Energy ◽  
High Temperature Phase ◽  
Unit Cell ◽  
Lattice Parameters ◽  
Temperature Phase ◽  
Hexagonal System ◽  
System A ◽  
Pyramidal Slip ◽  
Rhombohedral Boron

Boron is a semiconductor which has applications as a high energy fuel and coating material. Thus, one can assume there is an interest in the structural andelectronic properties. Boron has been found to crystallize into several structures. The α rhombohedral boron was reported to have lattice parameters of a = 5.057 A, α = 58°4. (hexagonal coordinates a = 4.908 A, c = 12.567 A) β Rhombohedral boron, the high temperature phase, has been found to have lattice parameters a = 10.145 A, α = 65° or in the hexagonal system a = 10.944 A, c = 23.811 A with 320 atoms per unit cell.

Nuclear magnetic resonance investigations of the structural phase transitions of AlPO4 tridymite

1995 ◽  
Vol 10 (10) ◽  
pp. 2586-2591 ◽  
Author(s):  
Yuehui Xiao ◽  
R. James Kirkpatrick
Keyword(s):  
High Temperature ◽  
Bond Angle ◽  
Structural Phase ◽  
Local Symmetry ◽  
Quadrupole Coupling Constant ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Temperature Structure ◽  
Bond Angles ◽  
Increasing Temperature

27Al and 31P NMR spectroscopic data are presented for the tridymite polymorph of AlPO4 (AlPO4−1) through its structural phase transition at about 80 °C. The RT 27Al and 31P spectra of AlPO4−t both contain doublets of broad peaks, indicating two well-separated groups of sites in the RT structure with mean Al-O-P bond angles per tetrahedron of ∼ 147.8°and 153.1°(±1). With increasing temperature, the doublets remain the same up to about 74 °C, where the relative intensities of the two peaks start to change. The peak corresponding to smaller Al-O-P bond angles disappears, and above ∼88 °C the 27Al and 31P spectra contain single symmetrical peaks, corresponding to a mean Al-O-P bond angle of 153.4°. This bond angle increases gradually with increasing temperature to 153.7°at ∼150 °C and remains constant to about 500 °C. 27Al quadrupole echo experiments suggests that the 27Al nuclear quadrupole coupling constant (QCC) is small and decreases with increasing temperature. QCC remains nonzero in the high temperature phase of AlPO4−t, consistent with the previously proposed 3m local symmetry of Al in the high-temperature structure.

scholarly journals The order/disorder phase transition of hypophosphorous acid H3PO2

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Martin Nastran ◽  
Berthold Stöger
Keyword(s):  
Phase Transition ◽  
Hydrogen Bonding ◽  
High Temperature ◽  
Low Temperature ◽  
Hydrogen Bonds ◽  
Rotation Axis ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Hypophosphorous Acid ◽  
Disorder Phase Transition

Abstract Hypophosphorous acid, H3PO2 is dimorphic with a phase transition in the 200–225 K range. The H3PO2 molecules are connected by hydrogen bonding to infinite chains extending in the [100] direction. In the high-temperature phase (P21212, Z ′ = 1 2 ${Z}^{\prime }=\frac{1}{2}$ ), the hydrogen bonds are disordered about a two-fold rotation axis. On cooling below the phase transition temperature, the hydrogen bonds become ordered, resulting in a symmetry reduction of the klassengleiche type of index 2. In the low-temperature phase (P212121, Z ′ = 1 ${Z}^{\prime }=1$ ), the c parameter is doubled with respect to the high-temperature phase. The hydrogen-bonding topology of the high- and low-temperature phases are double-infinite directed and undirected linear graphs, respectively.

Structural Study of TlH2PO4 and TlD2PO4 in the High Temperature Phase

1995 ◽  
Vol 5 (7) ◽  
pp. 763-769 ◽  
Author(s):  
S. Rios ◽  
W. Paulus ◽  
A. Cousson ◽  
M. Quilichini ◽  
G. Heger ◽  
...  
Keyword(s):  
High Temperature ◽  
Structural Study ◽  
High Temperature Phase ◽  
Temperature Phase

LATTICE DYNAMICS CALCULATIONS FOR SOLID BIPHENYL IN THE HIGH TEMPERATURE PHASE

1981 ◽  
Vol 42 (C6) ◽  
pp. C6-599-C6-601 ◽  
Author(s):  
T. Wasiutynski ◽  
I. Natkaniec ◽  
A. I. Belushkin
Keyword(s):  
High Temperature ◽  
Lattice Dynamics ◽  
High Temperature Phase ◽  
Temperature Phase

High temperature phase transitions and proton conductivity in some kdp-family crystals

1989 ◽  
Vol 100 (1) ◽  
pp. 135-141 ◽  
Author(s):  
A. I. Baranov ◽  
V. P. Khiznichenko ◽  
L. A. Shuvalov
Keyword(s):  
Phase Transitions ◽  
High Temperature ◽  
Proton Conductivity ◽  
High Temperature Phase ◽  
Temperature Phase
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