First-Principles Studies the Lattice Constants and the Electronic Structures of Diluted Magnetic Semiconductors (In,Mn)As

Lattice constants and electronic structures of diluted magnetic semiconductors （ In, Mn ） As were investigated using the first principles LMTO-ASA band calculation by assuming supercell structures. Three concentrations of the 3 d impurities were studied （ x = 1/2, 1/4, 1/8）. The effect of varying Mn coucentrations on the lattice constants and the electronic structures are shown.

Lattice Constant α Calculation of PZT Films Prepared by a New Modified Sol-Gel Method

PZT(Zr/Ti=52/48) ferroelectric films are prepared by a new modified Sol-Gel method from three stable-separated Pb2+, Zr4+, Ti4+ precursor–monomers. This method needs no distillation and has the advantage of easy change of the Pb2+/Zr4+/Ti4+ stoichiometric. In the paper we also investigate PT seeds influence on ferroelectric properties, crystallographic structures and surface morphologies, and find the bottom/up PT seeds structure prompte PZT crystallization and have superior ferroeletric properties. The paper introduce a method to deduce and calculate lattice constant α by ‘least square method’, then the more accurate lattice constant a0 can be got from X-ray diffractometer (XRD) analysis data. We also discover that grain sizes of PZT film calculated from XRD data are much closed to those of AFM, and the film a0 is relatively small due to crushing stress.

Microscopic insights into hydrophobicity of cerium oxide:Effects of crystal orientation and lattice constant

Cerium oxide possesses intrinsic hydrophobic properties ascribed to the unique electronic structure.However,the relationship between the crystal structure and hydrophobicity of cerium oxide has not been systematically studied.Herein,it is experimentally and theoretically demonstrated that the water contact angle(105.9°)of the(111)surface is higher than that(91.7°)of the(220)surface,associated with the lower surface free energy(28.44 mN/m)of(111)surface than that(38.48 mN/m)of(220)surface.Furthermore,cerium oxide films with(111)-terminated surface are annealed at 300℃ and 600℃ for1 h,respectively.The lattice constant increases(5.4594Å<5.4613Å<5.4670Å)with decreasing the annealing temperature(600℃>300℃>the as-deposited),leading to the increased water contact angle(96.7°<96.8°<99.0°).The First-principles calculation provides microscopic insights into the wetting mechanism,originating from the weakened adsorption capacity of the(111)surface for water molecules with the increasing lattice constant.

Modification of BCC phase and the enhanced reversible hydrogen storage properties of Ti-V-Fe-Mn alloys with varied V/Fe ratios

Ti-V-based alloys are proved of huge potential in storing hydrogen,but the incomplete reversible hydrogen storage capacity caused by overstability of V hydride has limited the large-scale application.In this study,Ti_(32)V_(40+x)Fe_(23-x)Mn_(5)(x=0,4,8,12,at.%)alloys were designed,and the effects of V/Fe ratio on phase constitution and hydrogen storage properties were investigated.The main phase of the alloys is body-centered cubic(BCC)phase,and the lattice constants of the BCC phase decrease with the decrease of V/Fe ratio.Moreover,C14 Laves phase exists in alloys with a Fe content of 19at.%to 23at.%.For hydrogenation,the C14 Laves phase can accelerate the hydrogen absorption rate,but the hydrogen absorption capacity is reduced.With the decrease of V/Fe ratio,the hydride gradually destabilizes.Owing to its large lattice constant and high hydrogen absorption phase content,the Ti_(32)V_(52)Fe_(11)Mn_(5)alloy shows the most enhanced hydrogen storage properties with hydrogenation and dehydrogenation capacities of 3.588wt.%at 298 K and 1.688wt.%at 343 K,respectively.The hydrogen absorption capacity of this alloy can be reserved to 3.574wt.%after 20 cycles of hydrogen absorption and desorption.

LATTICE PARAMETERS OF COMPLEX CARBONITRIDE CONTAINING Ti,Nb AND V

The lattice constants and chemical composition of Ti,Nb and V precipitates with different particle sizes have been measured hy means of CBED and EDAX.It was obtained that the concentration ratio Of Nb and V,C_(Nb)/C_V,and the lattice constants in the Nb-V steel de- crease with the decrease of the particle size of the precipitates,but there is no regularity for tattice constant of Ti,N b and V precipitate against their particle size in the Ti-V-Nb steel.

The Reciprocal Lattice in Hierarchic Quasicrystals

Initially, all that was known about diffraction in quasicrystals was its point group symmetry;nothing was known about the mechanism. The structure was more evident, and was called quasiperiodic. From mapping the Mn atoms by phase-contrast, optimum-defocus, electron microscopy, the progress towards identifying unit cell, cluster, supercluster and extensive hierarchic structure is evident. The structure is ordered and uniquely icosahedral. From the known structure, we could calculate structure factors. They were all zero. The quasi structure factor is an iterative procedure on the hierarchic structure that correctly calculates diffraction beam intensities in 3-dimensional space. By a creative device, the diffraction is demonstrated to occur off the Bragg condition;the quasi-Bragg condition implies a metric that enables definition and measurement of the lattice constant. The reciprocal lattice is the 3-dimensional diffraction pattern. Typically, it builds on Euclidean axes with coordinates in geometric series, but it also transforms to Cartesian coordinates.

Numerical analysis of acoustic band gaps in two-dimensional periodic materials

Using the plane-wave expansion (PWE)method , the band gaps of the two-dimension phononic crystals composed of square, triangle and honeycomb arrays aluminum cylinders in the air are calculated numerically. The band structures of three lattices were compared and analyzed. It is concluded that the band-gap of honeycomb lattices is located at lower frequency fields, compared with square and triangle lattices. When the filling fraction is between 0.091 and 0.6046, the honeycomb lattices have larger band gaps and gain an advantage over square and triangle lattices. In addition, the gap map is introduced to illustrate the influences of filling fraction on the number, the relative width and the limit frequency of the band-gap.

Electronic structures and properties of Ti, Zr and Hf metals

The electronic structures of pure Ti, Zr and Hf metals with hcp structure were determined by one atom (OA) theory. According to the electronic structures of these metals,their potential curves, cohesive energies, lattice constants, elasticities and the temperature dependence of linear thermal expansion coefficients were calculated. The electronic structures and characteristic properties of these metals with bcc and fcc structures and liquids were also studied. The results show that the electronic structures of Ti, Zr and Hf metals are respectively [Ar](3d n) 0.481 0 (3d c) 2.085 7 (4s c) 1.000 0 (4s f) 0.433 3 , [Kr](4d n) 0.396 8 (4d c) 2.142 8 (5s c) 1.262 0 (5s f) 0.198 4 , [Xe](5d n) 0.368 0 (5d c) 2.041 4 (6s c) 1.406 6 (6s f) 0.184 0 . It is explained why the pure Ti, Zr and Hf metals with hcp and bcc structures can exist naturally, while those with fcc structure can not.

Synthesis of AgGa_(1-x)In_(x)Se_(2) Polycrystalline Materials

AgGa_(1-x)In_(x)Se_(2)polycrystals were synthesized by the method of mechanical oscillation and temperature oscillation.X-ray diffraction spectra of polycrystal powder are conformable with the JCPDS cards.Lattice constants a and c calculated from the XRD were found to obey Vegard's law.The melting point of AgGa_(0.8)In_(0.2)Se_(2)obtained by means of differential scanning calorimetry(DSC)is 796.53℃.The DSC curve also show that there are no other transformation points below the melting point.The results indicate that polycrystalline materials synthesized by the method mentioned above are high-quality and can be used to grow single crystals by the vertical Bridgman technology.

Influence of sintering temperature on the thermoelectric properties of Ba_8Ga_(16)Si_(30) clathrate treated by spark plasma sintering

A series of Ba8Ga16Si30 clathrate samples were prepared by arc melting, ball milling, acid washing, and spark plasma sintering （SPS）. X-ray diffraction analysis revealed that the lattice of the Ba8Ga16Si30 samples expanded as the SPS temperature was increased from 400 to 750℃. Lattice contraction recurred when the SPS temperature was further increased in the range of 750-1000℃. This phenomenon can be explained by the variation of Ga content in the lattice. The thermoelectric figure of the merit ZT value of clathrates increased with the increase in SPS temperature and reached a maximum when the sample was subjected to SPS at 800℃. A further increase in SPS temperature did not contribute to the improvement of ZT. The variation of the lattice parameter a vs. SPS temperature T was similar to the variation ob-served in the ZT-T curve.

ELECTRONIC STRUCTURE AND PROPERTIES OF Au METAL

Using the new developed valence bond theory of metals,the electronic structure,crystal structure and physical properties of Au metal have been systematically analysed.It has been determined that its electronic structure is(5d_(n))^(4.65)(5d_(c))^(4.71)(6s_(c))^(0.62)(6s_(f))^(1.02).According to this electronic structure,lattice constant,cohesive energy.potential curve,bulk modulus and temperature dependence of liner thermal expansion coeCHcient have been calculated.The theoretical values of properties are all in good agreement with experimental results.This electronic structure has been verified in part by linear rigorous cellular method of band theory.It shows that the valence bond theory has been reached perfectly.

Structure and magnetic properties of Mn_(1.2)Fe_(0.8)P_(0.76)Ge_(0.24) annealed alloy

Bulk Mn_(1.2)Fe_(0.8)P_(0.76)Ge_(0.24) alloy was prepared by mechanical milling and subsequent spark plasma sintering technique.Effect of annealing on the structure and magneto-caloric properties of the alloy was investigated.XRD results show that both sintered and annealed samples possess a hexagonal Fe_2P-type crystal structure.After annealing,ferromagnetic impurity Fe_3Mn_4Ge_6,which exists in the sintered sample,was eliminated from the alloy.Furthermore,the lattice constants a and c change noticeably,leading to a decrease in c/a ratio,while the cell volume almost remains invariable.As a result,the Curie temperature of the alloy increases from 253 K to 298 K,but the maximum magnetic entropy change decreases from 37.5 to 11.7 J·kg·K^(-1) for 2 T magnetic field change.On the other hand,the thermal hysteresis of M-T curves around T_C upon heating and cooling is 14 and 8 K for the as-sintered and the annealed sample,respectively,showing evident change.

Linking anisotropy with Fe_3C distribution in AISI 1045 steel

The anisotropy of the microstructure, thermal expansion behavior, corrosion resistance and magnetic properties of AISI 1045 steel was investigated. The distribution of Fe3C lameUae in the investigation plane parallel to the radial directions of molds was observed to differ from that in the investigation plane perpendicular to the radial directions by transmission electron microscopy. The lattice constants a0 of α-Fe deduced from the XRD patterns of samples prepared using a sand （S）-mold and cut parallel to the radial direction of the mold （S//） and using a metal （M）-mold and cut parallel to the radial direction （M//）, the corrosion resistance measured using an electrochemical work- station, and the magnetic permeability obtained by vibrating sample magnetometry also indicated the existence of anisotropy in the tested samples. The anisotropic change of corrosion potential （Eeorr）, pitting potential （Epit） and magnetic permeability （μ） of the samples was observed to depend on the orientation factorF200 of α-Fe in the measured samples, which is controlled by the distribution of Fe3C lamellae in the eutectoid structure.

A Comprehensively Optimized Diagram in (Ga,In) (As,Sb) Reciprocal System

he expressions of the composition space and the dependent properties of the lattice constant, the energy bandgap and the Gibbs energy were presented for the (Ga,In)(As,Sb) quaternary compound semiconductor. On the basis of these expressions, a computer aided analysis system is set up for the design of ⅢⅤ compound semiconductor materials and growth processes. By using this system, a comprehensively optimized diagram is constructed through the projection of the optoelectronic properties (energy bandgap or wave length), in which the composition relations are matched to substrates and the miscibility gaps.

Experimental and first-principles investigation of crystal structure of powder metallurgy Al-1.1Sc and Al-2Sc alloys

Al-1.1%Sc and A1-2%Sc （mass fraction） alloys were prepared using gas atomized alloy particles. Samples from consolidated alloys were analyzed by XRD for the determination of lattice parameters. Using these lattice parameters, the mechanical properties of the alloys were calculated theoretically with WIEN2k and EMTO programs, respectively. The elasticity moduli of the experimentally produced alloys were compared with the theoretical calculation results. The calculated mechanical properties of A13Sc phase and A1-Sc alloys were discussed to determine the optimum Sc content of Al-Sc alloys. It may be concluded that the Sc content should be the maximum about 1.0%, much more Sc addition could not improve the mechanical properties of the alloys.

Influence of Gravity on Structure of Colloidal Crystal Using Simulated Microgravity

Liquid mixtures of water and deuterium oxide as the liquid phase, were used to match the density of charged colloidal particles. Kossel diffraction method was used to detect the crystal structures. The experiments under the density-matched （g=0） and unmatched （g=1） conditions are compared to examine the influence of gravity on the crystal structures formed by self-assembly of 110 nm （in diameter） polystyrene microspheres. The result shows that the gravity tends to make the lattice constants of colloidal crystals smaller at lower positions, which indicates that the effect of gravity should be taken into account in the study of the colloidal crystals.

Microstructure and Transformation on Platinum (111) Facets

The microstructures of platinum (111) facets were studied by reflection electron microscopy, and the features on facets, for example, growth steps, slip steps, and dislocations emerging through the surfaces, etc., were analysed. In the following annealing at about 1100°C for 1 h in the atmosphere, the migration of crystal surface atoms resulted in the transformation of stepped configuration on (111) facets. Differently high and sized 〈111〉 terraces or small planes distributed on facets constructed frustum structures.

Effects of GaN cap layer thickness on an AlN/GaN heterostructure

In this study, we investigate the effects of Ga N cap layer thickness on the two-dimensional electron gas（2DEG）electron density and 2DEG electron mobility of Al N/Ga N heterostructures by using the temperature-dependent Hall measurement and theoretical fitting method. The results of our analysis clearly indicate that the Ga N cap layer thickness of an Al N/Ga N heterostructure has influences on the 2DEG electron density and the electron mobility. For the Al N/Ga N heterostructures with a 3-nm Al N barrier layer, the optimized thickness of the Ga N cap layer is around 4 nm and the strained a-axis lattice constant of the Al N barrier layer is less than that of Ga N.

The Mechanical and Electronic Properties of Ternary Rare-Earth Hexaboride LaxNd8-xB6 (x = 0, 1, 7, 8) Materials

We have carried out density functional theory to study the lattice constants and electronic properties of LaB6, NdB6, Nd-doped LaB6, and La-doped NdB6. The lattice constant, intra-octahedral bond, inter-octahedral boron bond, and positional parameter (z) were calculated for LaB6, La7Nd1B6, La1Nd7B6, and NdB6. Our results show that the doped Nd increases the lattice constant of La7Nd1B6. Likewise, La-doping leads to an increase in the lattice constant of the La1Nd7B6. The PDOSs of LaB6, B of LaB6, La7Nd1B6, B of La7Nd1B6, La1Nd7B6, B of La1Nd7B6, NdB6, and B of NdB6 were calculated. La d-electron bands cross the Fermi energy, showing classical conductor behavior. The charge density results indicate that light and dark colors show high and low-intensity zones, respectively. La1Nd7B6 has a low-density region and LaB6 has a high-density region. The LaB6 midpoint has strong charge density peaks. Weak peaks are also observed for La1Nd7B6. Thus, ternary REB6 has good potential for many applications. This article reports an investigation of the electronic features and structural parameters of binary and ternary hexaborides.