Structural characterization of gel-grown neodymium copper oxalate single crystals

Sparingly soluble neodymium copper oxalate (NCO) single crystals were grown by gel method, by the diffusion of a mixture of neodymium nitrate and cupric nitrate into the set gel containing oxalic acid. Tabular crystal, revealing well-defined dissolution figures has been recorded. X-ray diffraction studies of the powdered sample reveal that NCO is crystalline. Infrared absorption spectrum confirmed the formation of oxalato complex with water of crystallization, while energy dispersive X-ray analysis established the presence of neodymium dominant over copper in the sample. X-ray photoelectron spectroscopic studies established the presence of Nd and Cu in oxide states besides (C2O4)(2-) oxalate group. The intensities of Nd (3d(5/2)) and Cu (2p(3/2)) peaks measured in terms of maximum photoelectron count rates also revealed the presence of Nd in predominance. The inductively coupled plasma analysis supports the EDAX and XPS data by the estimation of neodymium percentage by weight to that of copper present in the NCO sample. On the basis of these findings, an empirical structure for NCO has been proposed. The implications are discussed.

Synthesis and x-ray crystal structure of a CuII-theophylline complex: [Cu(theo)2 (H2O)3]·2H2O

The complex [Cu-II (theo)(2)(H2O)(3)].2H(2)O (theo = theophylline) was obtained from aqueous solution. The crystals belong to the monoclinic system, space group P2(1)/n, and are reflection twins about the (001) face. The structure was solved using data from a twinned crystal and refined to final R and R(W) values of 0.069 and 0.064, respectively. Copper has a square-pyramidal coordination with two thee molecules coordinating through N(7) at equatorial positions. The remaining sites are occupied by water molecules. O(6) of one of the thee molecules is at the other axial site at a longer distance of 3.18 Angstrom. This could lead to an alternate (4+1+1) octahedral coordination geometry for Cu-II. The packing is stabilized by stacking interactions between the theophylline moieties at an average separation of 3.46 Angstrom.

High-Throughput Study of the Cu(CH3COO)(2)center dot H2O-5-Nitroisophthalic Acid Heterocyclic Ligand System: Synthesis, Structure, Magnetic, and Heterogeneous Catalytic Studies of Three Copper Nitroisophthalates

A high-throughput screening was employed to identify new compounds in Cu(CH3COO)(2)center dot H2O-NIPA-heterocyclic ligand systems. Of the compounds identified, three compounds, Cu-3{(NO2)-C6H3-(COO)(2)}(3)(C3N6H6)] (1), Cu-2(mu(3)-OH)(H2O){(NO2)-C6H3-(COO)(2)}(CN4H)]center dot-(H2O) (II), and Cu-2(mu(3)-OH)(H2O){(NO2)-C6H3-(COO)(2}-)(CN5H2)]center dot 2(H2O) (III), have been isolated as good quality single crystals by employing conventional hydrothermal methods. Three other compounds, Cu-2{(NO2)-C6H3-(COO)(2)}-(CN4H)(H2O) (IIa), Cu-2{(NO2)-C6H3-(COO)(2)}(CN5H2) (IIIa), and Cu-2{(NO2)-C6H3-(COO)(2)}{(CN5H2)(2)}2H(2)O (IIIb), were identified by a combination of elemental analysis, thermogravimetric analysis (TGA), and IR spectroscopic studies, although their structures are yet to be determined. The single crystalline compounds were also characterized by elemental analysis, TGA, IR, UV vis, magnetic, and catalytic studies. The structures of the compounds have paddle wheel (I) and infinite Cu 0(H) Cu chains (II and HI) connected with NLPA and heterocyclic ligands forming two-(II) and three-dimensional (I and III) structures. The bound and lattice water molecules in 11 and 111 could be reversibly removed/inserted without affecting the structure. In the case of II, the removal of water gives rise to a structural transition, but the dehydrated phase reverts back to the original phase on prolonged exposure to atmospheric conditions. Magnetic studies indicate an overall antiferromagnetism in all of the compounds. Lewis acid catalytic studies indicate that compounds II and HI are active for cyanosilylation of imines.

Drug-drug co-crystals: Temperature-dependent proton mobility in the molecular complex of isoniazid with 4-aminosalicylic acid

Two drug-drug co-crystals of the anti-tuberculosis drugs isoniazid (INH), pyrazinamide (PYR) and 4-aminosalicylic acid (PAS) are reported. The first is the 1 : 1 molecular complex of INH and PAS. The second is the monohydrate of the 1 : 1 complex of PYR and PAS. The crystal structures of both co-crystals are characterized by a number of hydrogen bonded synthons. Hydrogen bonding of the COOH center dot center dot center dot N-pyridine type is found in both cases. In the INH : PAS co-crystal, there are two symmetry independent COOH center dot center dot center dot center dot N-pyridine hydrogen bonds. In one of these, the H-atom is located on the carboxylic group and is indicative of a co-crystal. In the second case, partial proton transfer occurs across the hydrogen bond, and the extent of proton transfer depends on the temperature. This is more indicative of a salt. Drug-drug co-crystals may have some bearing in the treatment of tuberculosis.

Synthesis and structure of La14V6CuO36.5: a transparent Cu(I) vanadate containing [OCuO](3-) sticks

The title compound, La14V6CuO36.5, was prepared from a stoichiometric mixture of La2O3,V2O5, and CuO at 1050-1080 degreesC. The compound forms transparent, pale green crystals and was characterized by wavelength dispersive spectroscopy and single crystal X-ray diffraction. The structure contains isolated VO43- tetrahedra and [OCuO](3-) sticks dispersed in a lanthanum oxide network. Films of La14V6CuO36.5 were grown on R-plane sapphire by using pulsed laser deposition. Rutherford backscattering spectroscopic and X-ray diffraction analyses of the films showed oriented growth of the title phase, a similar to5 eV optical band gap and n-type conductivity. The compound is an example of a transparent copper(I) oxide.

Synthesis of free standing nanocrystalline Cu by ball milling at cryogenic temperature

This paper reports for the first time synthesis of free standing nano-crystalline copper crystals of a similar to 30-40 nm by ball milling of copper powder at 150 K under Argon atmosphere in a specially designed cryomill. The detailed characterization of these particles using multiple techniques that includes transmission electron microscopy confirms our conclusion. Careful analysis of the chemistry of these particles indicates that these particles are essentially contamination free. Through the analysis of existing models of grain size refinements during ball milling and low temperature deformation, we argue that the suppression of thermal processes and low temperature leads to formation of free nanoparticles as the process of fracture dominates over possible cold welding at low temperatures. (C) 2012 Elsevier B.V. All rights reserved.

A surface energy model and application to mechanical behavior analysis of single crystals at sub-micron scale

Size effects of mechanical behaviors of materials are referred to the variation of the mechanical behavior due to the sample sizes changing from macroscale to micro-/nanoscales. At the micro-/nanoscale, since sample has a relatively high specific surface area (SSA) (ratio of surface area to volume), the surface although it is often neglected at the macroscale, becomes prominent in governing the energy effect, although it is often neglected at the macroscale, becomes prominent in governing the mechanical behavior. In the present research, a continuum model considering the surface energy effect is developed through introducing the surface energy to total potential energy. Simultaneously, a corresponding finite element method is developed. The model is used to analyze the axial equilibrium strain problem for a Cu nanowire at the external loading-free state. As another application of the model, from dimensional analysis, the size effects of uniform compression tests on the microscale cylinder specimens for Ni and Au single crystals are analyzed and compared with experiments in literatures. (C) 2009 Elsevier B.V. All rights reserved.

Study of noncollinear quasi-phase matching optical parametric amplification with group-velocity matching based on periodically poled crystals

The properties of noncollinear optical parametric amplification (NOPA) based on quasi-phase matching of periodically poled crystals are investigated, under the condition that the group velocity matching (GVM) of the signal and idler pulses is satisfied. Our study focuses on the dependence of the gain spectrum upon the noncollinear angle, crystal temperature, and crystal angle with periodically poled KTiOPO4 (PPKTP), periodically poled LiNbO3 (PPLN), and periodically poled LiTaO3 (PPLT), and the NOPA gain properties of the three crystals are compared. Broad gain bandwidth exists above 85 nm at a signal wavelength of 800 nm with a 532 nm pump pulse, with proper noncollinear angle and grating period at a fixed temperature for GVM. Deviation from the group-velocity-matched noncollinear angle can be compensated by accurately tuning the crystal angle or temperature with a fixed grating period for phase matching. Moreover, there is a large capability of crystal angle tuning.

组合外加电场提高Fe：LiNbO3中90°记录体全息的衍射效率

针对90°全息记录结构的特殊性，在记录和读出阶段分别施加不同极性的外加电场，实现了Fe：LiNbO3晶体中高衍射效率的全息记录和读出。在库赫塔列夫（Kukhtarev）方程基础上引人两维耦合波理论，对组合外加电场提高掺铁铌酸锂晶体光折变特性的机理进行了探讨。实验和理论计算结果都表明这种分别在记录和读出过程施加不同极性组合的外加电场是在Fe：LiNbO3中实现高衍射效率90°记录结构体全息的有效技术方案。

LiNbO3：Ru晶体的光折变特性研究

采用丘克拉斯基法生长了单掺杂的LiNbO3：Ru晶体，并对其作氧化处理。实验研究了LiNbO3：Ru晶体二波混频条件下光栅记录特性和波长的依赖关系；并且研究了氧化处理对其透射谱和光栅记录特性的影响。研究结果表明，LiNbO3：Ru晶体的最佳记录波长为458nm；氧化处理会增加LiNbO3：Ru晶体对光的吸收，同时提高光栅记录的灵敏度和饱和衍射效率，表现了不同于LiNbO3：Fe晶体的氧化态依赖特性。分析认为，LiNbO3：Ru晶体的反常氧化态依赖特性可能是由于出现了电子通道效应的暗衰减机制，以及Ru存在多

Local thermal fixing of a photorefractive LiNbO3 hologram by use of a CO2 laser

A real-time, in situ fixing method by use of heating with a CO2 laser beam is suggested for thermal fixing of a small local hologram in the bulk of a Fe:LiNbO3 photorefractive crystal. For heating up to 100 degrees C-200 degrees C a volume with a shape similar to that of the laser beam a heat-guiding technique is developed. On the basis of the heat-transfer equations, different heating modes with or without metal absorbers for heat guiding-obtained by use of a continuous or pulsed laser beam are analyzed. The optimal mode may be pulsed heating with absorbers. On this basis experiments have been designed and demonstrated. It is seen that the fixing process with CO2 laser beam is short compared with the process by use of an oven, and the fixing efficiency is quite high. (C) 1998 Optical Society of America.

Prescription for optimizing holograms in LiNbO3 : Fe : Mn

The photorefractive holographic dynamics of grating formation in photochromic doubly doped LiNbO3:Fe:Mn crystal is studied numerically and analytically in terms of the two-center model of Kukhtarev Et al. [Ferroelectrics 22, 949 (1979)]. The relations among the recorded and fixed space-charge fields and the doping densities, the oxidation-reduction states of the fields, and the intensities of UV-sensitizing and red recording beams are studied. Important conditions and effects are feued, and an optimal prescription for material doping and oxidation-reduction processing is suggested in which the crystal can be strongly oxidized and the Mn-doping density is smaller than the Fe-doping density. (C) 2000 Optical Society of America. OCIS codes: 050.7330, 190.5330, 090.2900.

Effect of absorption on the diffraction efficiency in Fe : LiNbO3 crystal with 90 degrees recording geometry

In this paper the saturated diffraction efficiency has been optimized by considering the effect of the absorption of the recording light on a crossed-beam grating with 90 degrees recording geometry in Fe:LiNbO3 crystals. The dependence of saturated diffraction efficiency on the doping levels with a known oxidation-reduction state, as well as the dependence of saturated diffraction efficiency on oxidation-reduction state with known doping levels, has been investigated. Two competing effects on the saturated diffraction efficiency were discussed, and the intensity profile of the diffracted beam at the output boundary has also been investigated. The results show that the maximal saturated diffraction efficiency can be obtained in crystals with moderate doping levels and modest oxidation state. An experimental verification is performed and the results are consistent with those of the theoretical calculation.

Electrochromism accompanying ferroelectric domain inversion in congruent RuO2 : LiNbO3 crystal

Electrochromic phenomena accompanying the ferroelectric domain inversion in congruent RuO2-doped z-cut LiNbO3 crystals at room temperature are observed in experiments. During the electric poling process, the electrochromism accompanies the ferroelectric domain inversion simultaneously in the same poled area. The electrochromism is completely reversible when the domain is inverted from the reverse direction. The influences of electric field and annealing conditions on domain inversion and electrochromism are also discussed. We propose the reasonable assumption that charge redistribution within the crystal structure caused by domain inversion is the source for electrochemically oxidation and reduction of Ru ion to produce the electrochromic effect. (c) 2005 Optical Society of America.

Quantitative measurement of domain inversion in RuO2 : LiNbO3 crystal by digital holographic interferometry

We quantitatively study the domain inversion in a RuO2:LiNbO3 crystal wafer by the digital holographic interferometry. The crystal wafer is placed into one arm of a Mach-Zehnder-type interferometer to record a series of holograms. Making use of the angular spectrum backward propagation algorithm, we reconstruct the optical wave field in the crystal plane. The extracted phase difference from the reconstructed optical wave field is a well linear function of the applied external voltage. We deduce that the linear electro-optic coefficient of the detected RuO2:LiNbO3 crystal sample is 9.1x10(-12) m/V. An unexpected phase contrast at the antiparallel domain wall is observed and the influence of the applied external voltage on it is studied in detail. Also the built-in internal field is quantitatively measured as 0.72 kV/mm. (c) 2006 American Institute of Physics.