Thermal atomic vibrations in Cu-Ni alloys

Copper radiation has been used in an x-ray study of the temperature dependence of the effective characteristic x-ray temperature _p(T) for the alloys of the Cu-Ni system over the temperature range 293–1073 °K and in a determination of the concentration dependence of d ln_p/dT for the alloys. It is shown that _p(c) is additive. The concentration dependence of d ln_p/dT is linear. The agreement between the experimental results and data in the literature is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 75–80, September, 1970.     

The effect of isotopic substitution on the thermodynamic properties of palladium-hydrogen alloys

An attempt has been made to predict the thermodynamic properties of the Pd-D and Pd-T systems from those of the Pd-H system. By considering only the isotopic dependence of the optic modes, a satisfactory interpretation of the infinitely dilute solutions is not possible. However, using only the isotopic dependence of the optic modes together with an empirical equation for the infinitely dilute solution yields calculated results for the concentrated solutions in both the single and two phase regions which are in excellent agreement with the experimental results for the deuteride and tritide systems.     

Molecular dynamics analysis of nanoimprinted Cu-Ni alloys

The nanoimprinted behaviors of Cu-Ni alloys were studied through molecular dynamics simulation. The results from the simulations showed that the punching force and the internal energy of the specimen increased rapidly with increasing punch position and both of they at the elevated temperature were lower than that at the low temperature. The punching force of the specimen with a lower Ni content was higher than that with a higher Ni content, while the internal energy of specimen was reverse. In addition, the spring-back phenomenon was more obvious with increasing Ni components of Cu-Ni alloy after the punch was retrieved during the nanoimprinting process and that induced a smaller residual stress within the specimens.     

Calculation of the thermodynamic properties of noble-metal alloys in the model electron-density functional method

The thermodynamic properties of the stable and metastable phases of theCu−Au, Ag−Au, andCu−Ag systems have been calculated in the representation of the many-body interatomic interaction potential within the framework of the model electron-density functional method. The calculated values of the thermodynamic properties are in good agreement with experimental data and help explain the laws of alloy formation in the given systems. Factors that affect the magnitude of the tetragonal distortion of theL1 ₀ structure of equiatomic alloys have been investigated. The possibility of a transition by the Bayne scheme from theL1 ₀ structure toB2 for alloyCuAu upon application of an external uniaxial [001] stress is discussed. Institute of Strength Physics and Materials Science, Siberian Division of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, p. 9–19, May, 1997.     

Local magnetic moment calculation in random Cu-Ni and Fe-Cr alloys

A simple method to calculate the local magnetic moments in random binary alloys has been developed within the Coherent Potential Approximation. Such a method has been applied to the case of Cu-Ni and Cr-Fe ferromagnetic alloys. The results have been compared with the experimental data obtained from neutron scattering experiments.     

Mixing and magnetic properties of surface alloys: The role of the substrate

In this paper, we have performed ab initio density functional theory calculations to compare the miscibility and magnetic properties of two-dimensional binary surface alloys of the form M_xN_1−x (M = Fe or Co; N = Pt, Au, Ag, Cd or Pb) on two different substrates - Rh(1 1 1) and Ru(0 0 0 1). The trends in miscibility for the two substrates are found to be strikingly similar. The magnetic moments show qualitatively similar behavior, but their magnitudes differ: surface alloys on Rh(1 1 1) have larger magnetic moments than on Ru(0 0 0 1). We infer that strain plays the determining role in stabilizing these two-dimensional alloys, whereas the differences in magnetic moments can be ultimately attributed to the different number of d-electrons in Rh and Ru.     

Enhanced diffusion due to neutron irradiation in Cu-Ni alloys at different temperatures

The review of the existing data on the reverse annealing of boron implants in silicon is given. The idea of the exchange reaction of boron substitutionals with silicon selfinterstitials as being responsible for the phenomenon is critically considered. Instead, the possible involvement of oxygen and oxygen-related secondary defects is proposed.     

MnPd合金相变，弹性和热力学性质的第一性原理研究

运用基于密度泛函理论第一性原理方法研究了MnPd从立方顺磁到四方反铁磁的相变以及其弹性性质和热力学性质等．结果表明：MnPd合金顺磁立方B2结构在施加了四方应变后,结构不稳定,会发生结构相变形成四方顺磁结构．四方顺磁相弹性稳定,然而在考虑了磁性后,反铁磁四方相比四方顺磁相能量更低,而且弹性和动力学都稳定,说明反铁磁四方相是MnPd的低温结构．从而得出MnPd合金的相变路径为两步：先发生结构相变从顺磁B2立方结构转变为顺磁四方相,再由磁性诱发相变形成反铁磁四方结构．通过准谐近似得到了摩尔比热容,德拜温度等热力学性质．     

The role of magnetic clusters in mictomagnetic alloys

The average moment and the concentration of magnetic clusters in $\text{Cu}$-Mn alloys were determined from magnetization data. Both are increased by aging. Magnetic clusters are responsible for most of both the extremely large steady field susceptibility at 4.2°K after zero-field cooling and the alternating low-field susceptability at its peak.     

First-principles investigations on thermodynamic properties of the ordered and disordered Si0.5Ge0.5 alloys

The structure, formation energy, and thermodynamic properties of Si_0.5Ge_0.5 alloys are investigated through first-principles method. The ordered and disordered structures of Si_0.5Ge_0.5 compounds are considered. Our results show that thermodynamic instabilities of Si_0.5Ge_0.5 alloys at 0 K can be judged from the calculated formation energy. However, the alloy might be prepared at specified environment owing to the entropy effects considered. Moreover, the temperature dependence of the heat capacity, Debye temperature and thermal expansion coefficient of ordered and disordered structures are discussed.     

Calculations of the thermodynamic properties for binary hcp alloys with simple embedded atom method model

The simple embedded atom method model for hcp metals developed by Johnson has been applied to calculate the thermodynamic properties of all binary alloy systems for the eleven transition hcp metals. It has been shown that the agreement with the calculation results from Miedema thermodynamic theory and with the available experimental data is general good, but the agreement with the experimental data for the formation energy of Co-Y alloys is weak, which implies that a more better model for hcp metals is needed.Project supported by the National Natural Science Fundation     

High-density properties of hard spheres within a modified Percus-Yevick theory: The role of thermodynamic consistency

Using an integral-equation approach based upon an approximation for the tail function, the equilibrium properties of a system of hard spheres are studied with special concern for the behavior in the region of close packing. The closure adopted is such that full, internal consistency is ensured in the thermodynamics of the model with respect to both the two zero-separation theorems as well as to the more standard virial and fluctuation routes to the equation of state. The scheme also makes use of the continuity properties of the tail function and of the cavity distribution function at contact. These properties are explictly tested in the low-density limit up to the fourth derivative. The theory generates an equilibrium branch bounded on the high-density side by a point corresponding to a packing fraction0.78, a value which closely matches Rogers' least upper bound for the densest packing of spheres. The pair structure of the fluid in the state of random close packing is also compared to the type of local order predicted by the theory at similar densities.     

The hyperfine properties of iron-gallium alloys

The hyperfine properties at Fe site in iron-gallium alloy are calculated using the full-potential linear-augmented-plane-waves method. We have calculated the Fermi contact field (B_hf) and isomer shift (δ) at the Fe site versus the number of neighbouring Ga atoms. We found that B_hf decrease whereas δ increases with increasing number of neighbouring G atom. In addition we have calculated the hyperfine properties of FeGa system with DO₃ structure, where various distributions of 4 the Ga atoms in the conventional unit cell are considered (including the regular DO₃ structure). We found that the DO₃ structure has the lowest energy as compared to the other configurations. The two distinct A and D sites of the ordered DO₃ conventional unit cell have two distinct values for B_hf and δ. On changing the atomic arrangement of the Ga atoms within the conventional unit cell, the configuration of the A site is maintained whereas that of the D site becomes imperfect. The contact magnetic hyperfine fields of the D-like sites in the imperfect structures are lower than that of the DO₃D site.