Icosahedral short-range order in deeply undercooled metallic melts

Experimental evidence of icosahedral short-range order in stable and deeply undercooled melts of pure metallic elements is obtained using the combination of electromagnetic levitation with neutron scattering. This icosahedral short-range order is shown to occur in the bulk metallic melt independently of the system investigated. It strongly increases with the degree of undercooling.     

X-ray investigation of short-range order in the liquid eutectic alloy Bi-Cd-Sn

From an analysis of the curves of the intensity of x-ray scattering and the atomic radial distribution function, information has been obtained about the formation of a complex polystructure in a liquid Bi-Cd-Sn melt near the melting point. The hypothesis is proposed that in the most probable structure of the liquid eutectic Bi-Cd-Sn alloy, in the neighborhood of the melting point, there are microscopic orbital regions containing bismuth atoms and microscopic regions with a statistical distribution of cadmium and tin. As the temperature is raised, this atomic distribution changes, and a homogeneous atomic solution is formed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 7–10, March, 1975.     

钴和铁熔体短程序的分子动力学模拟

通过分子动力学模拟研究了金属钴和铁熔体从普通液态到过冷液态普通微观结构的性质.所计算两体分布函数与可获得的实验结果基本一致,从普通液态到过冷液态的局域结构中的原子配位数为11和12的分布几率随着温度的降低而变小,而原子的配位数大于12的分布几率反而增加,角分布函数位于55.有一个明显的峰,位于110°有一个宽展的峰,位于150°有一个肩膀,表明金属钴和铁熔体的微观局域结构要比规则的二十面体团簇的结构复杂得多.我们的模拟结果表明金属熔体中的二十面体短程序随着温度的降低而增加,并在过冷液态中而占优势.     

Propagation of short-range order in the lattice gas

The lattice gas model is examined to make a comparison between the superposition approximation and one which is free from the approximation as long as the three-body distribution is concerned. The formulation is applied to the type I superionic conductor, AgI, in which Ag-ions can move like the atoms in liquid and give rise to a strongly correlated Ag-ion distribution over available lattice sites. The oscillatory behavior of the radial distribution function is found up to the seventh neighbor distances including three maxima and three minima. The degree of disordered arrangement is then examined by calculating the latent heat of transition from the ordered β-phase to disordered α-phase of the superionic conductor.     

Atomic short-range order in CuMn alloys

The establishment of atomic short-range order (SRO) has been investigated in CuMn alloys (5, 8,13,16,20 at. % Mn) by measurement of the electrical resistivity during isochronal and isothermal annealing. An increasing degree of SRO is accompanied by a reduction of resistivity; this effect increases with Mn concentration. For 8,13 and 16 at. % Mn SRO kinetics turn out to deviate significantly from single exponential behavior with a maximum at 13 at. % Mn, whereas at 5 and 20 at. % Mn SRO is adjusted in a single exponential process. For data analysis three methods are used: a sum of two and three exponentials as well as a log-normal spectrum of relaxation times. The strong interaction between second-nearest-neighbor atoms in CuMn seems to be essential for SRO kinetics but of minor importance for the value of SRO-induced resistivity change.     

Icosahedral short-range order in amorphous alloys

We have characterized the icosahedral short-range order in amorphous solids using local environment probes. Such topological local order is pronounced even in an amorphous alloy that does not form quasicrystalline phases upon crystallization, as demonstrated by the extended x-ray absorption fine structure and x-ray absorption near-edge structure of a Ni-Ag amorphous alloy analyzed through reverse Monte Carlo simulations.     

Investigation of short-range order in magnesium-terbium alloy

Using the model potential method with Ashcroft form factors, we predict the existence of short-range order in the alloy Mg−2.9 at. % Tb, which is experimentally confirmed by diffuse x-ray scattering. We use the diffuse x-ray scattering method to determine the characteristic temperature of the alloy: θ _D = 325 K. M. V. Lomonosov Moscow State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 26–30, July, 1996     

Calculation of short-range order in the method of cluster components

A scheme is proposed for calculating the short-range order in the method of cluster components for an n-component solid solution, taking into account an arbitrary number of spheres. The calculation of a single-, two-, and three-coordination spheres for a binary system and a calculation of a single sphere for a triple system are considered in detail. In the case of a binary system the possible type of property-composition dependence for a random distribution of the atoms in the case of one, two, and three coordination spheres are analyzed. The method is illustrated using a calculation of the concentration dependence of the elasticity constants of a KI_cBr_1-c solid solution.     

Polarization bremsstrahlung study of short-range order in solids

Possibility to elaborate a new method of the diagnostics of short range order in solids based on spectral measurements of polarization bremsstrahlung from relativistic electrons moving in a sample is shown. The main advantage of the method being proposed consists in the absence of distortions in desired function of atom radial density in distinction to that determined by the basic Zernicke-Prins approach based on angular measurements of scattered quasi-monochromatic X-rays.     

Twinning and short-range order in ordered titanium monoxide

Electron diffraction was used to study the annealed titanium monoxide TiO_1.087 containing the monoclinic ordered phase Ti₅O₅. The diffraction pattern of titanium monoxide in the (112)* _B1 plane of the reciprocal lattice of the parent B1 cubic structure contains not only structural, superstructural, and additional reflections but also a system of planar diffuse strips. It has been established that part of the additional reflections are twins of the superstructure reflections of the monoclinic ordered phase; the twinning plane is the ( $\overline 1 \overline 1 1$ ) plane of the reciprocal lattice of the parent cubic phase. The diffuse scattering contours cover finite plane areas in the reciprocal space characterized by the wave vectors K ₁₀₀ ～ ± (h + 0.07)k ₁₀₀, K ₀₁₀ ～ ±(k + 0.07)k ₀₁₀, and K ₀₀₁ ～ ±(l + 0.07)k ₀₀₁ in the B1 structure. The diffuse scattering is caused by short-range displacement order. Short-range substitution order and the corresponding diffuse scattering are absent.     

Control of lasing in biomimetic structures with short-range order

We demonstrate lasing in photonic amorphous structures that mimic the isotropic nanostructures which produce noniridescent color in nature. Our experimental and numerical studies reveal that lasing becomes most efficient at certain frequencies, due to enhanced optical confinement by short-range order. The optimal lasing frequency can be tuned by adjusting the structure factor. This work shows that lasing in nanostructures may be effectively improved and manipulated by short-range order.     

Equilibrium values of short-range order in gold-silver and gold-palladium-alloys

In previous papers the influence of quenching and annealing treatments on the electrical resistivity of alloys has been measured and interpreted as influence of the quenched-in vacancies upon kinetics of short-range order formation. In the present paper it is investigated under which conditions values corresponding to the equilibrium of short-range order can be found. It has been shown that such equilibrium values can be obtained only in a temperature range limited to both sides and that this range can be checked and extended by suitable combinations of heat treatments. The resistivity values measured for Au-Ag and Au-Pd alloys are discussed from this point of view.     

Modeling of short-range order in a defect square lattice

The short-range order and pair correlations in a square lattice in which some part of sites are occupied by A atoms and the other are vacant have been investigated by computer simulation. It is shown that, in the presence of interactions in the first coordination sphere of an A _y □_{1 ? y} solid solution with a square lattice, induced pair correlations damp only in the ninth coordination sphere. A functional dependence between the correlation in the first coordination sphere and the induced correlations in the next coordination spheres has been established for different compositions of the solid solution.