Band model for order-disorder transition in equiatomic binary alloys

In equiatomic binary alloys, by using simple approximations on a model hamiltonian (synthesis of those of Hubbard and Soven with interatomic interactions) we conclude that the order-disorder transition is generally sharper than with the Ising model, and can even be of first order.     

Heats of formation of binary transition metal alloys

The heats of formation of disordered transition metal alloys are related to moments of the density of states within an analytical tight-binding model for the d band. The difference in bandwidth and in energy levels between the metals are two dominant effects on alloying. The d charge transfer is evaluated in a self consistent way from the knowledge of the partial densities of states.     

Multiatom interactions,order and stability in binary transition metal alloys

Interface delocalization or depinning transitions such as wetting or surface induced disorder are considered. At these transitions, the correlation length for transverse correlations parallel to the surface diverges. These correlations are studied in the framework of Landau theory. It is shown the t^–1/2 at all types of transitions for systems with short-range forces wheret measures the distance from bulk coexistence.     

The atomic parameter model for the fifth and sixth transition metal quasicrystal alloys(Mc=0.5)

The forming ability of quasicrystal phase has a relationship with the atomic bond factors based on differences in atom size and electron factors.Usually,those factors or their combination are used to describe the forming ability,stability of alloys,etc.In this paper,the quasicrystal alloy forming abilities for the fifth and sixth transition metals(Y,Zr,Nb,Mo,Ru,Rh,Pd and La,Hf,Ta,W,Re,Os,Ir,Pt) based alloys have been studied by the size factor and the atomic parametric function.It has been found that an ell...     

Atomic ordering and ferromagnetism in binary alloys

Atomic and magnetic ordering in binary alloys are studied within the mean field approximation. The influence of magnetism on the spatial order-disorder critical temperature and, conversely, the influence of chemical order on the Curie temperature are analyzed in detail. Phase diagrams for various cases are presented. In particular we find that the interplay of the two order parameters yields in some cases unusual sequences of phases as a function of temperature. For example we obtain a possible sequence with increasing temperature of spatially ordered ferromagnet → spatially ordered paramagnet → spatially disordered ferromagnet → disordered paramagnet.     

Theory of solid solubility for rare earth metal based alloys

Both parabola and ellipse separating schemes are used to study the solid solubilities for the binary alloy systems based on the 13 rare earth metals. It has been found that the soluble elements can be separated from the insoluble ones by a parabolyy ₁=a?bx ₁ ² or an ellipse(x ₂?m)²/c²+(y₂?n)²/d²=1. The results show that the overall reliabilities of the solid solubilities for the 897 binary alloys based on the rare earth metals are 89.2% and 92.8% for the parabola and ellipse regularities respectively. The constants a and b in the parabola equation, andm, n, c andd in the ellipse equation are discussed, which can be related to some appropriate parameters for each host metal respectively.     

Theory of solid solubility for rare earth metal based alloys

Both parabola and ellipse separating schemes are used to study the solid solubilities for the binary alloy systems based on the 13 rare earth metals. It has been found that the soluble elements can be separated from the insoluble ones by a parabolyy ₁=a−bx ₁ ² or an ellipse(x ₂−m)²/c²+(y₂−n)²/d²=1. The results show that the overall reliabilities of the solid solubilities for the 897 binary alloys based on the rare earth metals are 89.2% and 92.8% for the parabola and ellipse regularities respectively. The constants a and b in the parabola equation, andm, n, c andd in the ellipse equation are discussed, which can be related to some appropriate parameters for each host metal respectively.     

Physical and mathematical model of the surface segregation in binary alloys of transition metals

The surface segregation in binary alloys of transition metals based on platinum and palladium with different surface-face orientations are simulated via the electron-density functional method. The concentrations of the surface-active components of the binary alloys and displacements of the surface ion planes thereof are calculated self-consistently. The influence of surface segregation and lattice relaxation on the surface energy and electron work function on the surface of alloys of transition metals with various concentrations is investigated. The simulation results are compared with experimental data.     

On the electrical resistivity of noble based transition metal dilute alloys

We apply the CPA expression of the electrical conductivity to the case of Au-based alloys containing 3d and 4d transition impurities. In this approach, a s-diagonal disorder larger for the 3d case than for the 4d one can explain the measured differences in resistivity between these two cases.     

Electronic theory for the metal-non-metal transition in simple metal alloys

The metal-non-metal transition in liquid alloys such as Cs_1–x Au _x and Li_1–x Pb _x is explained as resulting from concentration dependent electron charge transfer causing short range atomic order and a change from metallic to ionic bonds. Numerical results for the electronic density of states, the electron charge transfer, the free energy of mixing and the volume change are given.     

Noncollinear magnetic structures in binary alloys of transition elements

Concepts [1–4] are developed on these structures for A–B alloys having antiferromagnetic interaction between the individual local magnetic moments . The following cases are considered: 1) the exchange integrals I_AA > 0, I_BB < 0, I_AB > 0, while _A and _B are dependent on the composition; 2) I_AA > 0, I_BB < 0, I_AB < 0; _A, _B = const. Models are used to calculate the mean atomic magnetic moment for Co-Cr, Co-Mn, and Ni-Cr alloys. The agreement with experiment is satisfactory.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, Vol.12, No. 1, pp. 96–102, January, 1969.     

Coherent potential approximation to order-disorder transition in binary alloys

A band theory of order-disorder transition in an AB alloy is studied using the locator formalism in the coherent potential approximation. The influence of the difference in the band widths of A and B metals on the transition temperature is discussed.     

A molecular orbital model for the electronic structure of transition metal atoms in silcate and aluminate alloys

Applied to transition metal oxides and silicate and aluminate alloys, a classification scheme that separates non-crystalline dielectrics into three groups with different amorphous morphologies, demonstrates a direct correlation between stability against crystallization and oxygen atom coordination. It also provides a local bonding model for molecular orbital (MO), calculations that are based on the coordination and symmetry of transition metal atoms and the orbital energies of their oxygen neighbors. These calculations provide important insights into the electronic structure of transition metal dielectrics, e.g. the role of anti-bonding d-states in determining conduction band offset energies with respect to Si.     

Magnetovolume effects in transition metal alloys near the critical composition for ferromagnetism

Results of magnetovolume studies are presented on intermetallic compounds and binary alloys with weakly ferromagnetic properties of the following compositions: Ni₃Al, ( )₃Ga, Ti(Fe, Co), (Ti, Al)Co, Ni-Pt and Pd-Ni. Data for the pressure dependence of the spontaneous magnetization at 4.2 K and the shift of the Curie temperature with pressure follow roughly the realtions that can be derived in the model for weak itinerant ferromagnetism in most of the investigated systems. Invar-type of anomalies in the thermal expansion have already been observed in several cases. Experimental values for the magnetovolume parameter are derived and compared with theoretical predictions in the Stoner model.     

Charge transfers in complex transition metal alloys ()

We introduce a new Non-Orthogonal Tight-Binding model, for complex alloys, in which electronic structure is characterized by charge transfers. We give the analytic calculation of a charge transfer, in which overlapping two-center terms are rigorously taken into account. Then, we apply numerically this result to an approximant phase of a quasicrystal of alloy. This model is more particularly adapted to transition metals, and gives realistic densities of states. Received: 7 July 1997 / Revised: 10 March 1998 / Accepted: 3 April 1998     

Superconducting properties of amorphous transition metal alloys

We have co-sputtered amorphous films of several Mo and W-based superconducting alloys. Measurements of T_c, ($\text{d}\text{H}{}_{\mathrm{c2}}\text{d}\text{T}$)_Tc and the normal state resistivity near T_c were made on a number of these alloys. Our results and other data from the literature are studied to examine the correlation between T_c and the dressed density of states at the Fermi level.     

Electronic structure of amorphous transition metal alloys

The electrical resistivity, the Hall coefficient and the magnetic susceptibility of amorphous alloys (Metglass 2826A, Allied Chemical) have been measured above room temperature. The experimental data show strong similarities with liquid alloys.