Structural,electronic,optical,elastic properties and Born effective charges of monoclinic HfO_2 from first-principles calculations

First-principles calculations of structural, electronic, optical, elastic, mechanical properties, and Born effective charges of monoclinic HfO2 are performed with the plane-wave pseudopotential technique based on the density-functional theory. The calculated structural properties are consistent with the previous theoretical and experimental results. The electronic structure reveals that monoclinic HfO2 has an indirect band gap. The analyses of density of states and Mulliken charges show mainly covalent nature in Hf-O bonds. Optical properties, including the dielectric function, refractive index, extinction coefficient, reflectivity, absorption coefficient, loss function, and optical conductivity each as a function of photon energy are calculated and show an optical anisotropy. Moreover, the independent elastic constants, bulk modulus, shear modulus, Young＇s modulus, Poisson＇s ratio, compressibility, Lam6 constant, sound velocity, Debye temperature, and Born effective charges of monoclinic HfO2 are obtained, which may help to understand monoclinic HfO2 for future work.

The selective effect of food-grade guar gum on chalcopyrite-monoclinic pyrrhotite separation using mixed aerofloat(CSU11) as collector

The flotation separation of chalcopyrite from monoclinic pyrrhotite using food-grade guar gum(FGG) as a depressant was studied through flotation tests, kinetic studies, dynamic potential measurements, adsorption experiments, and infrared spectral analyses. The microflotation results showed that the flotation separation of chalcopyrite from monoclinic pyrrhotite could not be realized by adding mixed aerofloat(CSU11) alone. The depressant FGG exhibited a selective depression effect on monoclinic pyrrhotite by controlling the pulp pH range from 5.0 to 6.0, with a maximum floatability variation of 79.36% in the presence of CSU11. The flotation kinetics, zeta-potential, adsorption, and infrared spectroscopy studies revealed that the FGG could absorb more strongly on the surface of monoclinic pyrrhotite than on the surface of chalcopyrite. In addition, the results revealed that the interaction of FGG with the monoclinic pyrrhotite surface was governed primarily by strong chemisorption, whereas FGG mainly bonded to chalcopyrite through hydrogen bonding. This difference was responsible for the excellent depression selectivity of FGG toward monoclinic pyrrhotite flotation and weak depression effect toward chalcopyrite flotation.

Sintering of monoclinic SrAl_(2)Si_(2)O_(8) ceramics and their Sr immobilization

Monoclinic SrAl_(2)Si_(2)O_(8) ceramics for Sr immobilization were prepared by a liquid-phase sintering method.The sintering temperature,mineral phase composition,microstructure,flexural strength,bulk density,and Sr ion leaching characteristics of the SrAl_(2)Si_(2)O_(8) ceramics were investigated.A crystalline monoclinic SrAl_(2)Si_(2)O_(8) phase formed through liquid-phase sintering at 1223 K.The introduction of four flux agents(B_(2)O_(3),CaO·2B_(2)O_(3),SrO·2B_(2)O_(3),and BaO·2B_(2)O_(3))to the SrAl_(2)Si_(2)O_(8) ceramics not only reduced the densification temperature and decreased the volatilization of Sr during high-temperature sintering but also impacted the mechanical properties of the ceramics.Product consistency tests showed that the leaching concentration of Sr ions in the sample with flux agent B_(2)O_(3) was the lowest,whereas that of Sr ions in the sample with flux agent BaO·2B_(2)O_(3) was the highest.These results show that the leaching concentration of Sr ions depends largely on the amorphous phase in the ceramics.Meanwhile,the formation of mineral analog ceramics containing Sr is an important factor to improve Sr immobilization.

Monoclinic KNbO3 Nanowires for Photocatalytic Methane Production and Dye Degradation

The room temperature stabled monoclinic KNbO3 nanowires were found to act as photocatalyst for photocatalytic methane production and dye degradation in this work. Higher activities have been observed for monoclinic phase compared to the reference（orthorhombic phase）. In the photoreduction of CO2 reaction, the monoclinic KNbO3 nanowires exhibited a CH4 evolution rate of 0.025 μmol·g-1·h-1, which was higher than 0.021 μmol·g-1·h-1 of orthorhombic KNbO3 nanowires. In the photodegradation of rhodamine B（Rh B）, almost all the Rh B were degraded after 90 min light illumination for monoclinic KNbO3 nanowires. But for orthorhombic KNbO3 nanowires, the concentration of Rh B only decreased to 62% of the initial value.

Dispersion equation of magnetoelastic shear waves in irregular monoclinic layer

This paper studies the propagation of horizontally polarized shear waves in an internal magnetoelastic monoclinic stratum with irregularity in lower interface. The stratum is sandwiched between two magnetoelastic monoclinic semi-infinite media. Dispersion equation is obtained in a closed form. In the absence of magnetic field and irregularity of the medium, the dispersion equation agrees with the equation of classical case in three layered media. The effects of magnetic field and size of irregularity on the phase velocity are depicted by means of graphs.

Predicting Physical Properties of Tetragonal,Monoclinic and Orthorhombic M_3N_4(M=C,Si,Sn) Polymorphs via First-Principles Calculations

The recently discovered tetragonal, monoclinie and orthorhombic polymorphs of M3N4 （M=C, Si, Sn） are in- vestigated by using first-principles calculations. A set of anisotropic elastic quantities, i.e., the bulk and shear moduli, Young＇s modulus, Poisson ratio, H/G ratio and rickets hardness of M3N4 （M=C, Si, Sn） are predicted. The quasi-harmonic Debye model, assuming that the solids are isotopic, may lead to large errors for the non-cubic crystals. The thermal effects are obtained by the traditional quasi-harmonic approach. The dependences of heat capacity, thermal expansion coefficient and Debye temperature on temperature and pressure are systematically discussed in the pressure range of 0 IOGPa and in the temperature range of 0-1100 K. More importantly, o- C3N4 is a negative thermal expansion material. Our results may have important consequences in shaping the understanding of the fundamental properties of these binary nitrides.

Standard Enthalpy of Formation of Monoclinic Ammonium Paratungstate

The enthalpy of reaction for the decomposition of monoclinic ammonium paratungstate,(NH_4 )_10 H_2, W_12 O_424H_2 O(s), was measured using a HT-1000 calorimeter. From the experimentalresults, the standard enthalpy of formation of ammonium paratlingstate at 298.15 K is obtained.

Synthesis of Monoclinic Form of Gd_(2-x)Na_xCuO_4 by Direct Precipitation from Molten Salt

A new phase of Gd_(2-x)Na_xCuO_4 was synthesized by direct precipitation from the mixture of Gd_2O_3 and CuO in the molten KOH/NaOH/KNO_3 solution at temperature as low as 280℃. The resulting precipitate was characterized by using SEM, XRD, EDX, XPS and magnetic method. The XRD data indicate that the precipitated Gd_(2-x)Na_xCuO_4 is monoclinic with lattice parameters a=8.6816, b=3.7233. c=6.0796. a=γ=90', 0=108.75° and V=186. 13.

Effects of Oxygen Vacancy on the Electronic Structure of Monoclinic HfO_2 and Its Defect Energy States by the First Principles Calculation

The structural relaxation, electronic structures, formation energies and transition energy levels of monoclinic HfO2 with neutral and charged oxygen vacancies have been studied using the first principles calculation based on density-functional theory and generalized gradient approximation. The results show that oxygen vacancies with different charge states can be formed in m-HfO2 under both oxygen-rich and oxygen-poor conditions. Especially, lower formation energy is obtained in poor oxygen environment. In the presence of oxygen vacancies with different charge states, extra levels can be observed at different positions in the band gap. And the most stable charge states are obtained for varying Fermi levels in the HfO2 band gap. It is found that oxygen vacancy in m-HfO2 has a negative-U behavior.

G-Type Seismic Wave in Magnetoelastic Monoclinic Layer

This paper deals with the study of propagation of G type waves along the plane surface at the interface of two different types of media. The upper medium is taken as monoclinic magnetoelastic layer whereas the lower half-space is inhomogeneous isotropic. Dispersion equation and condition for maximum energy flow near the surface are obtained in compact form. The dispersion equation is in assertion with the classical Love-type wave equation for the isotropic case. Effect of magnetic field and inhomogeneity on phase velocity and variation of group velocity with scaled wave number has been depicted by means of graphs. It is observed that inhomogenetity decreases phase velocity and the magnetic field has the favouring effect. A comparative study for the case of isotropic layer and monoclinic layer over the same isotropic inhomogeneous half space has been made through graphs.

Molecular replacement study on form-B monoclinic crystal of insulin

The form-B monodinic insulin crystal was obtained from the sodium citrate buffer with 1% zinc chloride, keeping phenolic content between 0.76% and 1.25%. Its space group is P21, cell constants are: a = 4.924nm, b=6.094nm, c=4.818nm, β=95.8°. There are 6 insulin molecules which form a hexamer. The initial phase was obtained by using rotation function program of X-PLOR program package and molecular packing program of our laboratory. The molecular model was chosen from 4 zinc bovine insulin hexamer. After the preliminary refinement by using the rnacromolecular rigid body refinement technique, the molecular model was further refined and adjusted by using the energy-minimizing stereochemically restrained least-squared refinement on the difference Fourier maps. The finial R-factor is 214% at 0.3nm resolution, the r.m.s. deviations from standard bond length and bond angle are 0.0022nm and 4.7°, respectively.

TABLES OF SECOND-RANK ESTIMATED FORMULAS OF STRUCTURE SEMI-INVARIANT IN TRICLINIC AND MONOCLINIC SPACE GROUPS

In this report the second-rank estimated formulas of one phase structure semiinvariants of 15 space groups in triclinic and monoclinic crystal systems are given using the algebraic derivative method. These formulas may be used to determine the phases of structure factors in direct phase determination. The mathematical esti-

Preliminary Crystallographic Studies on a New Monoclinic Crystal Form of Phenol-Insulin

For a long time phenolic additions have been widely used for the preservation of insulin preparation, but its action mechanism has not been elucidated. In 1958 Schlichkrull first obtained monoclinic insulin crystals in a system with 1.0% phenol which differs remarkably from those crystal growing systems of rhombohedral 2Zn and 4Zn insulin. Kreyenbuhl and Rosenberg also reported in 1964 that the presence of either phenol or m-cresol is an absolute requirement for the formation of Zn

Anisotropy of laser emission in monoclinic Nd:ScYSiO_5 crystals cut along the optical indicatrix axes

In this Letter, we demonstrate the anisotropy of laser emission in disordered Nd：ScYSiO5 （Nd：SYSO） crystals cut along the optical indicatrix axes. High-powered lasers with different oscillation wavelengths and polariza- tions are realized by using different oriented crystals as gain media. For Y-cut crystals, the dual-wavelength laser vibration direction is found to be along the X axis and a maximum output power of 9.43 W is obtained, giving an optical-to-optical conversion efficiency of 48.8% and a slope efficiency of 51.3%. For X- and Z-cut crystals, 1075 and 1078 nm lasers operating orthogonally polarize oscillate with total output powers of 7.07 and 8.43 W, respectively. The experimental results reveal that the intrinsic anisotropy for the monoclinic disordered laser crystals could make laser design flexible and controllable.

Anisotropic optical and electric properties of β-gallium oxide

The anisotropic properties and applications ofβ-gallium oxide(β-Ga_(2)O_(3))are comprehensively reviewed.All the anisotropic properties are essentially resulted from the anisotropic crystal structure.The process flow of how to exfoliate nanoflakes from bulk material is introduced.Anisotropic optical properties,including optical bandgap,Raman and photolumines-cence characters are comprehensively reviewed.Three measurement configurations of angle-resolved polarized Raman spec-tra(ARPRS)are reviewed,with Raman intensity formulas calculated with Raman tensor elements.The method to obtain the Raman tensor elements of phonon modes through experimental fitting is also introduced.In addition,the anisotropy in elec-tron mobility and affinity are discussed.The applications,especially polarization photodetectors,based onβ-Ga_(2)O_(3)were summa-rized comprehensively.Three kinds of polarization detection mechanisms based on material dichroism,1D morphology and metal-grids are discussed in-depth.This review paper provides a framework for anisotropic optical and electric properties ofβ-Ga_(2)O_(3),as well as the applications based on these characters,and is expected to lead to a wider discussion on this topic.

The Structure and Properties of Multi-cations Doped KNN-based Piezoelectric Ceramics

The piezoelectric strain of K_(0.5)Na_(0.5)NbO_(3)-based lead-free ceramic at different temperatures was studied.The Rayleigh analysis shows that the intrinsic and extrinsic contributions are increased at temperature from 173 to 298 K.In addition,a monoclinic phase structure was observed at 83 K.The results of phase field simulation show that the temperature dependent microstructure evolution is a function of the local structure size.This work contributes to understanding the structure and properties relationship of the multi-cations doped KNN-based piezoelectric ceramics as a function of temperature.

A new transition metal diphosphideα-MoP_(2) synthesized by a high-temperature and high-pressure technique

Monoclinicα-MoP_(2),with the OsGe2-type structure(space group C2/m,Z=4)and lattice parameters a=8.7248(11)Å,b=3.2322(4)Å,c=7.4724(9)Å,andβ=119.263°,was synthesized under a pressure of 4~GPa at a temperature between 1100℃and 1200℃.The structure ofα-MoP_(2) and its relationship to other transition metal diphosphides are discussed.Surprisingly,the ambient pressure phase orthorhombicβ-MoP_(2)(space group Cmc21)is denser in structure thanα-MoP_(2).Room-temperature high-pressure x-ray diffraction studies exclude the possibility of phase transition fromβ-MoP_(2) to α-MoP_(2),suggesting thatα-MoP_(2) is a stable phase at ambient conditions;this is also supported by the total energy and phonon calculations.

Promoting effect of chloride ions on selective oxidation of methanol to methyl formate over zirconia-supported ruthenium oxide catalysts

The effect of chloride ions on a monoclinic ZrO2-supported RuOx （RuOx/m-ZrO2） catalyst with a Ru surface density of 0.3 Ru/nm2 was studied in the selective oxidation of methanol to methyl formate （MF） at a low temperature of 373 K. The m-ZrO2 support was Cl-free, and Cl- ions were introduced into the RuOx/m-ZrO2 catalyst by impregnation with zirconium oxychloride or ammonium chloride and subsequent thermal treatment in air at 673 K. The structures of these catalysts were characterized by X-ray diffraction, Raman and X-ray photoelectron spectroscopies. Their reducibility was probed by temperature-programmed reduction in H2. The RuOx domains were present as highly dispersed Rut42- structure on m-ZrO2 with similar reducibility for the RuOx/m-ZrO2 samples irrespective of modification with or without Cl ions. Introduction of appropriate amounts of zirconium oxychloride into RuOx/m-ZrO2 led to a remarkable increase in the methanol oxidation rate and MF selectivity, whereas introduction of ammonium chloride or zirconyl nitrate significantly inhibited the catalytic performance of RuOx/m-ZrO2. The promoting effect of Cl- ions derived from zirconium oxychloride can be tentatively attributed to their roles in facilitating the adsorption of methanol and desorption of MF product or its intermediates. This finding provides novel insights into the promoting effect of Cl- ions on oxides-based catalysts for selective oxidation reactions.

Pressure-Induced Metallization and Structural Phase Transition in the Quasi-One-Dimensional TlFeSe2

We report a comprehensive high-pressure study on the monoclinic TIFeSe2 single crystal,which is an antiferromagnetic jnsulator with quasi-one-dimensional crystal structure at ambient pressure.It is found that TIFeSe2 undergoes a pressure-induced structural transformation from the monoclinic phase to an orthorhombic structure above Pc≈13 GPa,accompanied with a large volume collapse of ΔV/V0=8.3%.In the low-pressure monoclinic phase,the insulating state is easily metallized at pressures above 2 GPa;while possible superconductivity with Tconset^2 K is found to emerge above 30 GPa in the high-pressure phase.Such a great tunability of TIFeSe2 under pressure indicates that the ternary AFeSe2 system(A=Tl,K,Cs,Rb) should be taken as an important platform for explorations of interesting phenomena such as insulator-metal transition,dimensionality crossover,and superconductivity.

Evaluation of zirconia–porcelain interface using X-ray diffraction

The aim of this study was to determine if accelerated aging of porcelain veneering had an effect on the surface properties specific to a tetragonal-to-monoclinic transformation（TMT） of zirconia restorations. Thirty-six zirconia samples were milled and sintered to simulate core fabrication followed by exposure to various combinations of surface treatments including as-received（control）,hydrofluoric acid（HF）, application of liner plus firings, application of porcelain by manual layering and pressing with firing, plus accelerated aging. The quantity of transformed tetragonal to monoclinic phases was analyzed utilized an X-ray diffractometer and one-way analysis of variance was used to analyze data. The control samples as provided from the dental laboratory after milling and sintering process had no TMT（X m5 0）. There was an effect on zirconia samples of HF application with TMT（X m5 0.8%） and liner plus HF application with TMT（X m5 8.7%）. There was an effect of aging on zirconia samples（no veneering） with significant TMT（X m5 70.25%）. Both manual and pressing techniques of porcelain applications reduced the TMT（manual, X m5 4.41%, pressing,X m5 11.57%）, although there was no statistical difference between them. It can be concluded that simulated applications of porcelain demonstrated the ability to protect zirconia from TMT after aging with no effect of a liner between different porcelain applications.The HF treatment also caused TMT.