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     

Role of magnetism in the formation of a short-range order in an Fe-Ga alloy

The formation of a short-range order in an Fe-Ga bcc alloy has been studied by Monte Carlo simulation with the use of effective interaction potentials calculated within the density functional theory for the ferromagnetic and paramagnetic states. It has been found that the pronounced short-range order of the D0₃ type is formed at Ga concentrations close to the boundary of the two-phase region at T < T _c, whereas no short-range order is observed at T < T _c. The results obtained are in agreement with the experimental X-ray diffraction analysis. The relation of the features of the short-range order in the Fe-Ga alloy to the magnetostriction value has been discussed.     

New theory of binary alloys with short-range order properties

A new method for treating the electronic structure of binary alloys is presented. It is based on the study of a finite size cluster connected at its edges to a Bethe-lattice of the same coordination number. An illustrative example is presented. It includes concentration sequences which are (i) random, (ii) with a tendency to segregation and (iii) with a tendancy to form binary compounds. Energy gaps and localized states appear naturally in the method.     

Effect of short-range order on thermo-emf of binary alloys

The thermo-emf of binary disordered alloys is calculated, taking into account correlations in the distribution of atoms of different kinds over the lattice. It is shown that the presence of short-range order in the alloys may lead to a nonlinear temperature dependence of the thermo-emf and cause a change in its sign.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 87–91, November, 1976.     

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.     

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.     

Chemical short-range order in Zr2Ni amorphous alloy

Extended X-ray absorption fine structure (EXAFS) and molecular dynamic (MD) simulation were used to study the short-range order in Zr₂Ni amorphous alloy. It is found that the bond length is significantly shorter for unlike atoms but longer for like atoms in amorphous state than that in the crystalline state. Meanwhile, the coordination number of Ni atom in amorphous structure is only half of that in ideal Zr₂Ni crystalline. Based on these results, we proposed that there exists Zr₂Ni-like chemical short-range order in the Zr₂Ni amorphous alloy.     

Property-composition correlations and short-range order in bcc and fcc binary solid solutions

The properties of an ordering solid solution are substantially dependent on the long-range and short-range order parameters; a method is given for representing a binary solid solution as a set of cluster components whose short-range order parameters are incorporated out to the second coordination sphere. The scheme is illustrated via the lattice parameter and Debye temperature for Ti-Mo alloys (bcc lattice) and via the magnetic moment of Fe-Pd alloys (fcc lattice). The method allows one to describe nonmonotonic composition-property relationships and to define the values of properties for ordered structures.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 18–24, February 1978.     

Annealing effects and short-range ordering in the non-magnetostrictive amorphous alloy Co58Ni10Fe5Si11B16

Effects of isothermal and isochronal annealing on the coercive field and the effective magnetic anisotropy in the as-quenched and the stress relieved amorphous alloy Co₅₈Ni₁₀Fe₅Si₁₁B₁₆ were investigated. The mechanisms of the deterioration of soft magnetic properties in non-magnetostrictive amorphous alloys by annealing at low temperatures,T _a <T _c , are discussed. It turned out, that short-range ordering, i.e., topological short-range ordering (TSRO) and chemical short-range ordering (CSRO), caused by annealing lead to changes of the magnetostriction _s , and of the induced magnetic anisotropyK _i . Both effects give rise to an increase of the coercive field. In addition, the kinetics of short-range ordering was studied and from these data, which are closely related to the stability of soft magnetic properties, the activation energy and a preexponential factor was derived:Q _s.r=0.7eV,v ₀=9.6×10³s^–1.     

Theory of ordering in binary substitution alloy with body-centered cubic lattice

With the framework of a second order approximation of the Kirkwood, a study has been made of ordering in binary substitution alloys with B2 structure. Interatomic interactions in the first and second coordination spheres have been taken into account. It has been shown that an order—disorder phase transformation can be of the first or second kind, depending on the ratio of the ordering energies in the first and second coordination spheres (w and ) and their composition. The calculated configurational thermal capacity in the region of the Kurnakov point agree well with experimental data for /w=0.25.S. M. Kirov Ural Polytechnical Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 93–96, September, 1993.     

The short-range order and ordering energies in gold-copper polycrystalline alloys that are rich in gold

The concentration dependence of the short-range order parameters in gold-rich polycrystalline disordered solid gold-copper solutions was investigated using the X-ray diffuse-scattering method. On the X-ray diffuse-scattering patterns of disordered alloys with 75, 83, and 90% gold, diffuse maximums that are typical of short-range order were absent in the region of the possible superstructure reflex (100), but in the region of the possible reflex (110), an intensity rise on the scattering patterns was revealed that noticeably depended on the gold concentration. The application of the method, taking the effects of static displacements on the considered coordination spheres into account, allowed the determination of short-range order parameters for nine coordination spheres. The spectra of short-range order parameters, which was calculated using the least-squares method, had the long-range sign-alternating representation that is inherent in the Cu₃Au superstructure. The absolute values of short-range order parameters were detected to decrease with an increase of the gold content in the alloys. The concentration dependence and small values of ordering energy of investigated polycrystalline alloys were revealed on the first coordination sphere using the Clapp-Moss method.     

Influence of the short-range order parameter on the optical properties of amorphous nickel-phosphorus alloy

The influence of the short-range order of amorphous nickel-phosphorus alloy on the IR absorption is studied. The relation between the optical properties and the microstructure of amorphous nickel-phosphorus alloys obtained by various technological methods is considered. It is shown that a coating of amorphous Ni−P alloy obtained by electrolytic deposition has the most homogeneous structure; this permits the use of such coatings as protective layers for optical and magnetic memory disks. Optical methods permitting the estimation of the dimensions of the microcrystalline regions in an amorphous matrix are outlined. T. Shevchenko Kiev University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 34–40. May, 1997.     

Influence of the local environment and short-range order on the heats of formation of binary alloys

The concentration dependences of the heats of formation (H(x)) of disordered binary alloys of iron and cobalt with titanium have been calculated in both the single-site approximation and with allowance for the local environment. The dependence of H of equiatomic alloys on the short-range order in the first coordination sphere is investigated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 62–66, August, 1980.     

Effect of short-range atomic order on macroscopic magnetic properties of equiatomic FePd alloy

X-ray diffraction, magnetic measurements, and Mössbauer spectroscopy were employed to comparatively analyse the relation of the basic characteristics of highly anisotropic materials– coercive force H_c and Curie temperature T_C to the peculiarities of short-range atomic order that forms upon annealing of disordered samples of equaiatomic FePd alloys produced by different techniques (casting, melt-spinning, severe deformation). It is shown that for all samples, independently of methods of their preparation, the ordered states with the maximal values of coercivity are inhomogeneous in the composition of short-ordered regions, type of atomic ordering, and degree of tetragonality. The Curie temperature depends on the temperature and duration of annealing for ordering similarly to the conventional course of coercivity, which is peculiar to these alloys. The behaviour of these macroscopic characteristics (H_c and T_C) in the course of annealing is shown to correlate with changes in the local atomic configurations revealed in the Mössbauer spectroscopy experiments.     

A multi-range order parameter for binary alloy bulk materials and nanoparticles

A multi-range order parameter for binary alloys is considered, valid for bulk materials and nanoparticles. The difference between two common definitions is discussed, arising when applied to small systems. Its properties are illustrated on the example of the order/disorder transitions in Au–Pd fcc bulk materials and nanoparticles. The thermodynamic equilibrium states of these systems are predicted by Metropolis Monte Carlo sampling in the canonical (NPT) ensemble and an embedded-atom model potential. Short range order is found partially preserved by the transition while long range order vanishes. The order of intermediate ranges is found to be particularly sensitive to the presence of anti-phase boundaries (APBs) in both, bulk alloys and nanoparticles.     

Bonding and short-range order effects in the theory of the electronic structure of liquids

A generalized coherent-wave approximation is suggested which takes into account the fact that the average environment of an atom in many liquids is not spherically symmetric but tends to have a point-group symmetry determined by its nearest neighbours. The effect of this generalization upon the theory of Phariseau and Ziman is discussed.