Interdiffusion of hydrogen and alkali ions in a glass surface

Experimental data on the interdiffusion of hydrogen and alkali ions in glass are examined using a concentration-dependent interdiffusion coefficient, taking into account surface dissolution. The comparisons between calculated and experimental concentration profiles and diffusion coefficients are more satisfactory than for a concentration-independent diffusion coefficient, and support the use of the interdiffusion coefficient.     

Rubidium hydrogen glutarate and ammonium hydrogen glutarate: X-ray studies of quasi-isostructural crystals involving very short hydrogen bonds

Rubidium and ammonium hydrogen glutarates (M ^{+ –}CO₂.C₃H₆.CO₂H) each crystallize with four molecules in orthorhombic unit cells of almost identical dimensions: (M = Rb)a = 18·55,b = 7·57,c = 5·29 Å; (M = NH₄)a= 18·59,b= 7·56,c= 5· 27 Å. They have very similar structures, but they are not isomorphous: space groupsCmma (Rb) andPmaa (NH₄).The crystal structures have been determined by three-dimensional X-ray analysis and refined with moderate precision. Both have infinite chains of glutarate residues, linked end-to-end by very short, symmetrical hydrogen bonds, with O···H···O = 2·40(2) (Rb) and O···H···O = 2·460(6) Å (NH₄).In the Rb salt, the glutarate residue has strict, crystallographicm symmetry. The difference in the NH₄ salt arises from small movements of the carbon and (especially) the oxygen atoms out of this symmetry plane. These are due to N-H···O bonding: two equivalent cations in the Rb salt, each making contact with eight oxygen atoms, become differentiated in the NH₄ salt by linkage to different sets of four oxygens.We wish to acknowledge financial support from the Science Research Council, and our indebtedness to Drs. J. G. Sime, K. W. Muir and others for help with KDF9 programs.     

Growth and characterization of a novel NLO crystal bis-glycine hydrogen chloride (BGHC)

Single crystals of bis-glycine hydrogen chloride (BGHC), a semiorganic nonlinear optical (NLO) material, have been grown by slow solvent evaporation technique. Good optical quality single crystals with dimensions up to 33×5×5 mm³ are obtained. The crystals are characterized by optical transmission spectrum, FTIR and X-ray diffraction studies. The thermal stability of the crystal is studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The second harmonic generation (SHG) efficiency of BGHC was found to be 5.6 times that of KDP. The laser damage threshold values studied in single shot mode indicates that BGHC crystal possesses a fairly high value of 9.8 GW/cm² and thus the NLO studies confirmed the superiority of BGHC over KDP and urea crystals. The dielectric constant of the crystal was studied as a function of frequency and the results are discussed.     

Network hydrogen bonding in two new cocrystals sustained by 731-1731-1731-1, a tetrahedral hydrogen bond donor

We report details of the synthesis and X-ray crystal structures of two new cocrystals that are sustained by the tetrahedral hydrogen bond donor [Mn(CO)₃(₃-OH)]₄. [Mn(CO)₃(₃-OH)]₄· 2(2,3,5,6-tetramethylpyrazine)·2H₂O·2MeCN,a=21.503(3),b=12.674(1),c=17.318(2), =102.15(2), C2/c,D _calc=1.46 mg/m³,Z=4,4188 observed reflns,R _f=0.047,R _w=0.040; 1.[Mn(CO)₃(₃-OH)]₄·4,4-dipyridyl·2MeCn,a=16.942(6),b=12.395(2),c=18.790(6), =114.88(3), C 2/c,D _calc=1.60 mg/m³,Z=4,2430 observed reflns,R _f=0.043,R _w=0.051;2. 1 crystallizes as a 2-D grid, whereas2 forms 1-D strands. The hydrogen bond patterns exhibited by1 and2 are analyzed in the context of our earlier studies involving [Mn(CO)₃(₃-OH)]₄ and other relevant literature.     

Structure determination and hydrogen bonding of 1-naphthoxyacetic acid, a potential plant growth hormone

1-Napthoxyacetic acid crystallizes in the centrosymmetric space group C2/c (No. 15) with cell dimensions of a=14.273(2)Å, b=5.845(1)Å, c=24.211(1)Å, =105.815(2)°. The structure of the title compound reveals a carboxyl group-naphthalene ring dihedral angle of 4.85(14)°, O—H- - -O hydrogen bonded dimer, hydrogen bond distance of 2.640(2)Å, hydrogen bond angle of 172(2)°, and a cis configuration of O2 (double bond) and O3 relative to the C11—C12 bond all of which indicate that the title compound may be effective as a plant growth hormone.     

Synthesis and crystal structure of a new two-dimensional chromium(III) network through hydrogen bonds

A new chromium(III) complex, [Cr(ox)(bdmpza)(H₂O)], (ox = oxalate dianion and bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate, respectively), has been synthesized and characterized by X-ray crystallography. This compound crystallizes in the monoclinic space group P2₁/c, with a = 7.008(3) Å, b = 14.229(5) Å, c = 16.497(7) Å, = 101.588(7)°, V = 1611.5(11) ų, Z = 4. The chromium atom has a distorted octahedral environment with different coordination atoms. Bis(3,5-dimethylpyrazol-1-yl)acetate anion is a tridentate ligand, and the oxalate group acts as a chelating bidentate ligand. This compound also forms an infinite two-dimensional network through O–H O hydrogen bonds. The lengths of the hydrogen bonds are 2.765(5) and 2.733(5) Å, respectively.     

Crystal and molecular structure of cesium hydrogen malonate

The title compound is C₃H₃O₄Cs, CsHM, monoclinic,P2₁/c,a=8.393 (3),b=7.960(2),c=9.023(2) Å,=92.11(2)°. The structure was solved by the heavy-atom method and refined by least-squares techniques to anR factor of 0.023 for 760 observed reflections. The CsHM has no internal symmetry and one carboxy group, but not the other, is twisted almost at right angles (96°) to the plane of the three central carbon atoms. The hydrogen malonate anions are linked together by two short and symmetrical O-HO hydrogen bonds [2.468(4) and 2.482(4) Å]. The structure consists of hydrogen malonate chains cross-linked by the Cs⁺ ion. The IR spectrum of CsHM has been analyzed.     

Charge state and hydrogen diffusion in Ti-based alloys

The electronic structure, charge state, and hydrogen diffusion in icosahedral Ti-based alloys have been investigated by the methods based on the density-functional theory. The charge state of the hydrogen atom in Ti₃₆Zr₃₂Ni₁₃ has been determined for different types of tetrahedral voids. The charge state of hydrogen atoms in Ti₃₆Zr₃₂Ni₁₃, Ti₃₆Hf₃₂Ni₁₃, and Ti₄₈Zr₈Fe₁₈ is calculated for the ratio H/M = 1.7, where H is the number of hydrogen atoms and M is the number of metal atoms. It is established that hydrogen atoms in all objects studied are in an almost neutral state. The hydrogen diffusion coefficient is determined for Ti₃₆Zr₃₂Ni₁₃.     

Solution and solid-state hydrogen bond patterns ofo-methoxy- ando-ethoxybenzoic acids

The hydrogen bond patterns ofo-alkoxybenzoic acids have been shown previously to involve intramolecular hydrogen bonds. In this paper we show thato-methoxybenzoic acid (I) and o-ethoxybenzoic acid (II) both exist as monomers with intramolecular hydrogen bonds in solution but that, in the solid-state,I crystallizes as hydrogen-bonded dimers whileII crystallizes with an intramolecular hydrogen bond. The correlation between solution and solid-state hydrogen bond patterns is made using solution and solid-state IR and NMR methods and by correlating the solid-state patterns with known X-ray crystal structures. The crystal structure ofI is reported here. Crystal data: monoclinicP2₁/n;a=7.002(2),b=14.945(9),c=7.719(4) Å,=115.44(3)°,Z=4,V=729.4 ų, andR=0.046 (1660 reflections).     

Crystal and molecular structure of putrescinium hydrogen phosphate dihydrate

The X-ray structure of putrescinium hydrogen phosphate dihydrate, , has been determined from three-dimensional diffractometer data and refined by full-matrix least-squares techniques. The crystals are monoclinic,P2₁/c, a=6.5932(4),b=16.776(1),c=9.2375(7) Å,=95.772(6)°, andZ=4; finalR=0.036 for 1360 observed reflections. The putrescinium dication has the all-trans conformation. The structure contains a three-dimensional network of H bonds in which all available proton do nors are utilized. Each of the groups interacts with three electron-rich atoms arranged in an equilateral triangle, but the character of the individual N-HO bonds is different at opposite sides of the dication. The water molecules are involved in relatively strong H bonds but they do not interact with the cation.Systematic name: 1,4-butanediammonium hydrogen phosphate dihydrate.     

Interdiffusion of hydrogen and alkali ions in glass surfaces

The Boksay-Doremus theory on the interdiffusion of hydrogen and alkali ions in glasses was extended by taking into account the association of hydrogen ions and non-bridging oxygen ions. In the derivation of the interdiffusion coefficient the bulk composition of the glass is taken into account. Theoretical concentration profiles were compared with experimental data, reported in literature, of alkali-alkaline earth-silicate glasses and of a sodium-aluminium-silicate glass. An essential feature of this extended B-D theory is, that the relative order of chemical durability of alkaline earth containing glasses is found by this theory without assuming excessive changes in individual diffusion coefficients.     

Structure and disorder in schultenite,lead hydrogen arsenate

The structure of lead hydrogen arsenate has been studied by pulsed neutron single crystal diffraction. The structural parameters obtained agree well with the best available X-ray data. In addition, the hydrogen atom positions and disorder have been well characterized, yielding potentially important information regarding hydrogen atom potentials.     

Growth and physical properties of a new chiral open-framework crystal for NLO applications: Cesium hydrogen l-malate monohydrate

Cesium hydrogen l-malate monohydrate, CsH(C₄H₄O₅)·H₂O, is a new chiral open-framework semi-organic crystalline material with a second-harmonic generation efficiency one order of magnitude greater than KDP. Single crystals of this new material have been grown by the conventional slow cooling technique from aqueous solution. Grown crystals display both platy and prismatic morphologies depending on the imposed supersaturation. Hardness values measured using Vickers hardness indenter show considerable anisotropy. The resistivity behavior at room temperature and above, places the crystal between an ionic conductor and a dielectric. The single-crystal SHG efficiency estimated through Maker fringes experiment gives d_eff which is 4.24 times that of KDP. Single and multiple shot experiments performed on the grown crystals for the fundamental and second harmonic of pulsed Nd:YAG laser (1064 and 532 nm) show that it exhibits a high laser damage threshold which is a favorable property for nonlinear optical applications.     

Conditions of oxygen/hydrogen sterility

A new additional condition that is necessary and sufficient for diamond crystallization-a stringent requirement for extremely low activity of both oxygen and hydrogen in the crystallization environment-is introduced. It is proposed to refer to this requirement as the condition of oxygen/hydrogen sterility (OHS). A number of its new and important consequences are revealed.     

Electrically conducting glasses produced by ion exchange and hydrogen treatments

Electrically conducting layers have been induced in some alkali-containing silicate glasses by subjecting them to a Na⁺?Ag⁺ ion-exchange reaction followed by a reduction treatment in hydrogen. The surface resistances of the ion-exchanged and reduced glasses range from 0.15ohm/square to 4.1 ohm/square depending on the glass composition. Most of the layers give TCR values around 2000 ppm/K. The microstructural studies of the ion-exchanged and reduced layers confirm that such high surface conductances arise due to the formation of continuous chains of metallic silver and bismuth droplets in a glass matrix.     

The thermodynamics of water and hydrogen solubility in fused silica

A statistical thermodynamic model of the solubility of water vapor in glass is developed as an extension of previous models of monatomic and diatomic gas solubility in glass. The model predicts the $\text{p}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ dependence of water vapor solubility in fused silica and indicates the binding energies of dissociated H and OH species to be about ?63 and ?99 kcal/mol, respectively. The OH binding energy is found to be slightly temperature dependent, namely E_OH(0) = ?81.3?0.0163T. The tendency of chemical solubility of H₂ to predominate over physical solubility above 500°C correlates with the model equations for H₂ solubility.     

Synthesis and crystal structure of the iridium(I) carbene complex with a pair of hydrogen wing tips

The iridium(I) cyclooctadiene complex with two (3-tert-butylimidazol-2-ylidene) ligands [(H-Im^tBu)₂Ir(COD)]⁺PF₆^? (C₂₂H₃₂PF₆IrN₄) has been prepared, and its crystal structure is determined by X-ray diffraction. Complex exhibits slightly distorted square planar configurations around the metal atom, which is coordinated by two H-Im^tBu ligands and one cyclooctadiene group. The new iridium carbene complex has a pair of hydrogen wing tips. The Ir?C_carbene bond lengths are 2.066(5) and 2.052(5) Å, and the bond angle C?Ir?C between these bonds is 95.54(19)°. The dihedral angle between two imidazol-2-ylidene rings is 86.42°.     

Synthesis and characterization of ferroelectric magnesium hydrogen phosphate single crystals

Ferroelectric Magnesium Hydrogen Phosphate MgHPO₄ (MHP) single crystals are grown by slow diffusion of magnesium chloride in sodium metasilicate gels impregnated with orthophosphoric acid. Bright and transparent prismatic, tabular, and isometric habit MHP crystals upto 3 × 2 × 1 mm³ are obtained. Results of chemical, X-ray diffraction, EDAX, microhardness and magnetic analysis are reported. The average etch pit density is determined by chemical etching to be 7 × 10³ cm⁻². Microtopographic investigations revealed the mechanism of crystal growth.     

Supramolecular liquid crystals displaying competitive hydrogen bonding: Small molecule mesogens assembled through different hydrogen bond assemblies

A series of supramolecular assemblies created through competitive hydrogen bonding of a n-alkoxy benzoic acid hydrogen bond donor and a mixture of hydrogen bond acceptors: a liquid crystal-forming rigid bi-pyridyl and a non-mesogenic tetrafunctional pyridyl species. The associative chain structures displayed mesogenic characteristics at loadings dependent on the concentration of the disruptive tetrafunctional agent- systems eliminated liquid crystallinity at 85% inclusion in heating transitions and 90% in cooling. The assembled structures displayed considerable mesophase stability. This was observed through long liquid crystalline lifetimes even at high compositions of 4PD, which generally dampened due to a generalized eutectic effect. It is believed that the freedom of mobility inherent in the C8 Acid allows for the reorganization of the hydrogen bonds in the liquid crystalline state providing for a very high loading of disruptor and long mesophase lifetimes.