Analysis of Gibbsian Segregation at Heterophase Cu-MnO Interfaces

An alternative methodology to analyze Gibbsian segregation at heterophase interfaces with transmission electron microscopy (TEM) is presented and discussed. In this approach the actual concentration of the segregating element in a monolayer at the interface is obtained. This is in contrast to line scans or maps where the concentrations determined are a convolution of the concentration profiles with the electron probe and where for general interfaces the deconvolution problem can not be solved accurately. This is possible because the present approach uses explicitly the information offered by hetero-interfaces. The method is tested on the possible segregation of indium and gallium dissolved in a Cu matrix to interfaces between MnO precipitates and the Cu matrix. The occurrence of indium segregation is clearly demonstrated and the In concentration in the terminating Cu monolayer at the parallel {111} Cu/MnO interface is determined to be 15 ± 3 at.%, whereas the average In concentration in the Cu matrix is 3.8 ± 0.4 at.%. Further it was found that indium effectively blocks gallium segregation towards the oxide side of the interface. On the other hand, the presence of gallium does not influence the segregation of indium. Explanation for the gallium segregation at the oxide side relies on a thin spinel type Ga _x Mn _y O₄, which reduces the misfit at the metal-oxide interface.     

Evaluating the electric property of different crystal faces and enhancing the Raman scattering of Cu2O microcrystal by depositing Ag on the surface

The surface electric property of Cu₂O microcrystal affects the interaction of facets with substance in the aqueous solution, and hence plays a key role in determining the photocatalytic activity. In this paper, the capability of Cu₂O microcrystals with exclusive {111}, {110} or both lattice surfaces in reducing Ag⁺ to Ag⁰ were investigated. Ag particles selectively deposited on {111} surfaces of Cu₂O, while not on {110} surfaces. The different behaviors of the two surfaces are mainly attributed to their different electric properties: negatively-charged {111} surfaces absorb Ag⁺ ions while positively-charged {110} surfaces repel them. Raman scattering of Cu₂O {111} surfaces was enhanced by the photo-deposition of Ag particles.     

The topography of nickel crystals during the reaction towards Ni(CO)4; A field ion microscope study

The structural aspect of the formation of Ni(CO)₄ by the reaction of CO with solid nickel has been studied. The nickel initial state was a nearly hemispherical single crystal as prepared by field evaporation of a nickel field emitter tip. Field-free reaction of CO with the clean nickel surface took place at pressures up to 2 mbar, reaction times up to 45 h, and at a temperature of 373 K, which as a result from work by others was found optimum for highest rates of Ni(CO)₄ formation. Neon field ion imaging at 80 K after reaction with CO showed the crystal always in an intermediate state, which had the features: (1) Areas of {;111} were increased; (2) at half angles between a central (111) and peripherical {111} planes there were {110} planes flanked by {210}, and {100} flanked by {511}, respectively; (3) with the exception of the planes mentioned in feature (2), the remaining surface area was more than mono-atomically stepped. From these results and in accordance with the theory of crystal growth (Kossel, Stranski) and the theory of crystal dissolution (Lacmann, Franke, Heimann) a pure octahedron is expected to be the final state of the crystal. This implies that nickel atoms removed by the reaction are most frequently taken from 〈110〉 atom chains of the {111} planes.     

Study of yield stress anomaly of Fe2MnAl single crystal by in situ TEM straining

L2₁-structured Fe₅₉Mn₁₇Al₂₄ shows a yield stress anomaly with a peak yield stress at 700?K. The aim of the work reported here was to determine the dislocation mechanisms involved in this anomalous behaviour by performing in situ straining on Fe₅₉Mn₁₇Al₂₄ single crystals in a transmission electron microscope at 300–900?K. Cross-slip of ?111? dislocations was frequently found to occur between {110} and {211} planes at all temperatures tested. At 300?K, dislocations were four-fold dissociated and the partials moved together under stress. At 700–800?K, partial dislocations with a Burgers vector of a/2?111? dominated the deformation. These partial dislocations moved independently in the ordered matrix in a jerky manner, with rapid motion between long periods of locking. X-ray diffraction measurements showed that the degree of L2₁-order slightly decreased with increasing temperature in the range 300–700?K, and dropped rapidly above 700?K. At 900?K, the material was B2-ordered. The increased yield stress at elevated temperatures is primarily attributed to the uncoupling of a/2?111? partial dislocations trailing shear-induced anti-phase boundaries.     

Atomic-Scale Simulation Study of Equilibrium Solute Adsorption at Alloy Solid-Liquid Interfaces

Equilibrium structural properties of solid-liquid interfaces in Cu-Ni alloys are studied by Monte-Carlo simulations employing interatomic potentials based on the embedded-atom method. We describe a thermodynamic-integration approach used to derive bulk concentrations and densities for solid and liquid phases in two-phase thermodynamic equilibrium. These results are used as a basis for constructing three-dimensional supercell geometries employed in Monte-Carlo-simulation studies of solid-liquid interface properties for {100} and {111} crystallographic orientations. At a temperature of 1750 K (four percent below the calculated melting point of pure Ni) equilibrium density and concentration profiles have been derived, allowing a calculation of the relative Gibbsian adsorption, , of Cu (solute) relative to Ni (solvent) at solid-liquid interfaces in Ni-rich alloys. We derive absorption values of and –0.23 ± 0.50 atoms/nm² for {100} and {111} interfaces, respectively. These results are discussed in the context of available experimental measurements and continuum-theory results for adsorption at heterophase interfaces.     

Blocking-Effekte bei Transmission von α-Teilchen durch Germanium- und Siliziumkristalle

The energy loss of channeled and blocked α-particles of ThC transmitted parallel to the {111} and also the {110} planes of germanium and silicon was investigated. In the spectrum of the transmittedα-particles measured with a small-acceptance-angle detector, in addition to the random and normally channeled α-groups a separated group with a high energy loss was observed in the direction of the {111} planes, while in the direction of the {110} planes this group is not well separated from the randomα-group. A model is proposed which describes this high energy loss for observation in the direction of either plane. In agreement with this model a higher yield ofα-particles with high energy loss in the {111} planes in comparison with the {110} planes of germanium and silicon was measured.     

Si{111}晶面粒子堵塞坑的新现象

本文报道了从粒子背散射堵塞效应的实验中所发现的单晶Si的{111}晶面粒子堵塞坑的新现象。单晶Si的{111}晶面有两个面间距d_{(111)^(a)和d(111)^(b),而{110}晶面只有一个面间距d(110)。由此导致两者的堵塞坑是不同的,我们已从α粒子和质子的Si单晶堵塞效应的实验得到了证实。并由此估计了d(111)^(a)和d(111)^(b)以及d(110)的2ψ1/2角。据作者了解,到目前为止,国内外还没有人发现此现象。此现象的发现对复杂晶体的堵塞和沟道效应的研究开阔了前景。 关键词：}     

Investigations of EPR g Factors and Rhombic Distortion for the Rhombic Cu2+ Centers in K2Zn1?x Cu x F4 Crystals at Low Temperature

The electron paramagnetic resonance g factors g _i (i?=?x, y, z) of two rhombic Cu²⁺ centers, Cu²⁺(II) and Cu²⁺(III), in K₂Zn_1?x Cu _x F₄ crystals found at low temperature are calculated from the complete diagonalization (of energy matrix) method based on the cluster approach. The calculations show that the ground state wave function of the two rhombically compressed Cu²⁺ centers is $ | {d_{{z^{2} }} }\!\!> $ with a small admixture of $ | {d_{{x^{2} - y^{2} }} } \!\!> $ . The rhombic distortions for both Cu²⁺ centers are obtained from the calculations. The results are discussed.     

Atomic configuration of antiphase boundaries in alloys

Computer simulation methods in the approximation of pairwise interatomic Morse potentials are used to calculate the atomic configurations and the energy of formation of 1/2 <110> {111} antiphase boundaries in ordered Cu₃Au and Ni₃Fe alloys. Atomic displacements result in considerable smearing of the first five planes closest to an antiphase boundary and a slip of atomic planes. These effects substantially reduce the energy of formation of antiphase boundaries. The influence of the size factor on the atomic configuration on the antiphase boundaries is discussed.Translated from Izvestiya Vysshykh Uchebnykh Zavedenii, Fizika, No. 2, pp. 43–47, February, 1985.In conclusion, the authors express their thanks to A. I. Tsaregorodtsev for useful discussion of this work.     

Kinetic features of the oxide formation on {111} polar planes upon anode treatment of <Emphasis Type="Italic">n</Emphasis>-GaAs

The mechanism and kinetics of anode destruction of {111} polar planes of n-GaAs and morphological features of forming oxide films in the potentiostatic mode of polarization in weakly acid solutions of electrolytes have been studied. It has been found that anode polarization of the gallium plane (111) Ga provides the formation of a porous structure of both the single-crystal matrix and oxide film, which has a planar topology. In this case, the pore density is always commensurable with the surface dope concentration. In contrast to the gallium plane, the anode polarization of the arsenic plane \(\overline {\left( {111} \right)} \) As provides the tangential mechanism of destruction of the semiconductor matrix and the island-type morphology of the oxide. Equal crystallographic orientation of islands is determined by the directive action of the family of oxidized planes \(\left\{ {1\overline {11} } \right\}\) GaAs. However, regardless of the crystallographic orientation of the polar plane, the forming oxide is represented by polycrystalline As₂O₃ and amorphous Ga₂O₃.     

First-principles characterisation of the pressure-dependent elastic anisotropy of SnO2 polymorphs

Using DFT calculations, this study investigates the pressure-dependent variations of elastic anisotropy in the following SnO₂ phases: rutile-type (tetragonal; P4₂/mnm), CaCl₂-type (orthorhombic; Pnnm)-, α-PbO₂-type (orthorhombic; Pbcn)- and fluorite-type (cubic; Fm-3m). Experimentally, these polymorphs undergo sequential structural transitions from rutile-type → CaCl₂-type → α-PbO₂-type → fluorite-type with increasing pressure at 11.35, 14.69 and 58.22 GPa, respectively. We estimate the shear anisotropy (A₁ and A₃) on {1?0?0} and {0?0?1} crystallographic planes of the tetragonal phase and (A₁, A₂ and A₃) on {1?0?0}, {0?1?0} and {0?0?1} crystallographic planes of the orthorhombic phases. The rutile-type phase shows strongest shear anisotropy on the {0?0?1} planes (A₂ > 4.8), and the degree of anisotropy increases nonlinearly with pressure. In contrast, the anisotropy is almost absent on the {1?0?0} planes (ie A₁ ~ 1) irrespective of the pressure. The CaCl₂-type phase exhibits similar shear anisotropy behaviour preferentially on {0?0?1} (A₃ > 5), while A₁ and A₂ remain close to 1. The α-PbO₂-type phase shows strikingly different elastic anisotropy characterised by a reversal in anisotropy (A₃ > 1 to < 1) with increasing pressure at a threshold value of 38 GPa. We provide electronic density of states and atomic configuration to account for this pressure-dependent reversal in shear anisotropy. Our study also analyses the directional Young’s moduli for the tetragonal and orthorhombic phases as a function of pressure. Finally, we estimate the band gaps of these four SnO₂ phases as a function of pressure which are in agreement with the previous results.     

Bi12GeO20晶体的位错蚀斑与对称群

用化学浸蚀法系统的研究了Bi₁₂GeO₂₀晶体{100},{100},{111}等晶面独特浸蚀斑规律并用对称群理论进行分析.理论预示的蚀斑形态与实验结果符合很好.显示位错蚀斑是由{112}晶面组成,即晶体的惯态面为{112}.     

Epitaxial growth defects and interfacial structures of Cu deposited on TiO2

Epitaxial growth defects and the interfacial structure between vapor deposited Cu and TiO₂(110) have been studied by combined high-resolution electron microscopy (HREM) and image simulations. The Cu film was found to grow epitaxially with an orientation given by Cu(111)//TiO₂(110) and Cu110//TiO₂ [001]. With this relationship, there exist two equivalent domain orientations which are rotated with respect to each other by 180°. Localized misfit dislocations have not been detected, but {111} stacking faults and microtwins were observed which may occur as a result of 3-D island coalescence. HREM observations and image simulations have been used to study the interface atomic structure. The dominant interfacial structure has a stoichiometric (110) TiO₂ surface with bridging rows of O atoms and occasionally, an interfacial structure having a reduced (110) TiO₂ surface terminated by both Ti and O atoms has been observed locally.     

Pyroxene inclusions in paleo-Christian mosaic tesserae: a new tool for constraining the glass manufacturing temperature

The mineral inclusions of two orange glass tesserae from paleo-Christian mosaics were investigated in order to derive the melting temperature reached during their production (sourced from Padua and Vicenza, Veneto region, Italy). In particular, clinopyroxene crystals were studied by single-crystal X-ray diffraction and electron microprobe WDS analysis. The crystals show C2/c symmetry, typical of disordered Ca/Na and Mg/Al distributions indicating high-temperature of formation (>700°C). The cation site populations were obtained by combining results from the two experimental techniques enabled us to derive the following stoichiometric formula:

Crystallographic shear of polymorphic TiO<Subscript>2</Subscript> nanocondensates with enhanced Cr<Subscript>2</Subscript>O<Subscript>3</Subscript> dissolution via pulsed laser ablation

TiO₂ nanoparticles with enhanced solid solution of Cr up to 16 wt% in polymorphs of rutile, anatase, brookite, α-PbO₂-type, and occasionally baddeleyite-type were synthesized via pulse laser ablation on ceramic TiO₂ target dissolved with Cr₂O₃ or clamped Cr/Ti plates in air. Analytical electron microscopic observations indicated these nanocondensates have prevalent crystallographic shear (CS) along specific planes to form superstructures. The rutile type typically shows (100) and (010) CS besides the conventional ones rotating about the [111] zone axis as reported for ambient samples. The CS planes are parallel to (001) for anatase, (001) and ([`1] \overline{1} 10) for brookite, whereas (001) and {1[`3] \overline{3} 1} for the α-PbO₂-type TiO₂ with varied extent of Cr dissolution. Surface modification, as a result of Cr dissolution and/or internal stress, was observed for all the polymorphs.     

Spin-valve magnetoresistive structures based on Co/Tb multilayer films

The effect of the layer thickness on the magnetic properties of {Co/Tb}_n, {Co/Tb}_n/Co, and {Co/Tb}_n/Co/Cu/Co multilayer films is studied. The dependence of the hysteresis and magnetoresistive properties of {Co(1 nm)/Tb(1 nm)}_n/Co(5 nm)/Cu(L _Cu)/Co(5 nm) structures on the thickness of the {Co/Tb}_n layer and copper spacing are obtained. The feasibility of spin-valve structures based on {Co/Tb}_n multilayer films with in-plane anisotropy is demonstrated.     

Atomic configurations of antiphase boundaries IN Lla superlattice alloys: APB of 1/2 <110> {110} type

An antiphase boundary of 1/2 <100> {110} type in equilibrium with atomic displacements is examined, such as occurs in an ordered alloy with Ll₂ superlattice. The effects from discrepancies in the atomic radii are evaluated along with those from differences in atomic interaction in a parallel simulation of the lattice states near planar defects in ordered Cu₃Au and Ni₃Fe. It is found that there are substantial differences in the local deformations at these boundaries by comparison with other types of planar defect: there are parallel planes involving compression and stretching together with oscillating atomic displacements perpendicular to the boundary, which die away at the eighth plane from the APB. It is found that the region of local deformation out to which the continuum theory of elasticity does not apply extends to ten planes of {110} type.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 49–52, July, 1987.     

Ferromagnetic properties of cyclically deformed Fe3Ge and Ni3Ge

The magnetisation behaviour of cyclically deformed and non-deformed Fe₃Ge and Ni₃Ge is examined at sufficiently low temperatures below the Curie point. Despite these two intermetallics having the same L1₂ structure, they are found to show quite different behaviour in their ferromagnetic properties; the spontaneous magnetisation (M _S) remains unaffected in the former whereas it decreases notably in the latter after cyclic deformation. The origin of the difference is investigated and attributed to the difference in operative shear planes. These are mainly on {001} planes without the introduction of notable amounts of anti-phase boundary (APB) tubes in Fe₃Ge and mainly on {111} planes with the introduction of a high density of APB tubes composed of {111} APBs in Ni₃Ge. The effects of cyclic deformation on the high-field susceptibility?χ?and the coercive force (H _C) are also discussed by taking into account the dislocation distributions introduced by the {001} and {111} slips.     

The Transformations from the New Intermediate Entangled State

The new intermediate entangled state |η;θ〉 is proposed by virtue of IWOP technique, which is the common eigenvector of [([^(x)]₁ - [^(x)]₂)cosq-([^(p)]₁ - [^(p)]₂)sinq][(\hat{x}_{1} - \hat{x}_{2})\cos\theta -(\hat{p}_{1} - \hat{p}_{2})\sin\theta ] and [([^(x)]₁ +[^(x)]₂)sinq+ ([^(p)]₁ + [^(p)]₂)cosq][(\hat{x}_{1} +\hat{x}_{2})\sin\theta + (\hat{p}_{1} + \hat{p}_{2})\cos\theta ]. The squeezing transformation operator, Hadamard transformation operator, Fresnel transformation operator and Radon transform operator are constructed by |η;θ〉.     

Ab initio investigation on mechanical properties of copper

Employing the ab initio total energy method based on the density functional theory with the generalized gradient approximation, we have investigated the theoretical mechanical properties of copper (Cu) systematically. The theoretical tensile strengths are calculated to be 25.3 GPa, 5.9 GPa, and 37.6 GPa for the fcc Cu single crystal in the [001], [110], and [111] directions, respectively. Among the three directions, the [110] direction is the weakest one due to the occurrence of structure transition at the lower strain and the weakest interaction of atoms between the (110) planes, while the [111] direction is the strongest direction because of the strongest interaction of atoms between the (111) planes. In terms of the elastic constants of Cu single crystal, we also estimate some mechanical quantities of polycrystalline Cu, including bulk modulus B, shear modulus G, Young's modulus E_p, and Poisson's ratio ν.