Xiaolin Shu

Point-defect properties in body-centered cubic transition metals with analytic EAM interatomic potentials

Abstract Analytic embedded-atom method (EAM) interatomic potentials for body-centered cubic (bcc) transition metals have been constructed. The total energy is regarded as consisting of a pair potential part, an embedding interaction part and a modification term. All these parts are analytic functions of the atomic separations only and are fitted to various bulk properties, such as cohesive energy, vacancy formation energy, lattice constant and elastic constants. The present potentials are shown to predict a more realistic pressure–volume relationship so that interactions at separations smaller than that of the first-nearest neighbors can be treated. Interstitial formation energies are calculated for various configurations, using quenched molecular dynamics. Vacancy, surface and phonon spectra have been also studied and satisfactory agreement with available experimental data has been found.

Calculation of formation enthalpies and phase stability for Ru-Al alloys using an analytic embedded atom model

A simple analytic embedded atom model for hcp and fee metals is presented. Using such a model, the embedding functions, the potential functions and the modifying functions for hcp Ru and fcc Al are derived. The thermodynamic data, such as the dilute-limit heats of solution, formation enthalpies of disordered solid solutions and intermetallic compounds, for Ru-Al alloys are calculated. The results show that the calculations are comparable to the experimental data available and with the results calculated using the first principles and Miedemas theory. The calculations of the heats of formation of Al13Ru3, Al3Ru in the DO22 and DO3 structure type, Al2Ru in the C11b structure type and AlRu in the B2 structure type indicate that the trends in structural stability can be interpreted directly in terms of the formation energy

Calculation of thermodynamic properties of Mg-RE (RE = Sc, Y, Pr, Nd, Gd, Tb, Dy, Ho or Er) alloys by an analytic modified embedded atom method

Using the analytic modified embedded atom method (MEAM), the embedding, potential and modifying functions for the Mg and rare earth (RE) metals (RE = Sc, Y, Pr, Nd, Gd, Tb, Dy, Ho and Er) are presented. The thermodynamic properties, such as the dilute-limit heats of solution, enthalpies of formation of disordered solid solutions and intermetallic compounds, for the binary Mg-RE alloys are calculated. The obtained results are in good agreement with the available experimental data and with the results calculated using Miedema theory. The calculations of the enthalpies of formation of Mg3 RE, Mg2 RE, MgRE, MgRE2 and MgRE3 with various ordered structures (DO3 , DO19 , L12 , C15, MoPt2 , B2, W1 and L10 ) indicate that the trends in the structural stability can be interpreted directly in terms of the formation energy. Moreover, the lattice constants and volume contractions of alloys with various compositions are determined based on the relation between the formation energy and the interatomic distance. The correlation between the enthalpy of formation and volume contraction for intermetallic compounds is discussed.

Monte Carlo simulation of the surface segregation of Pt-Pd and Pt-Ir alloys with an analytic embedded-atom method

Using the analytic modified EAM potentials, the surface concentrations and concentration depth profiles of (111) and (10 0) faces of Pt-Pd and Pt-Ir binary alloys are studied with Monte Carlo simulation based on the grand canonical ensemble statistical rule. In Pt-Pd alloy, the topmost surface is enriched with Pd, and the subsurface layer is depleted of Pd. The simulation results show a damped oscillation of Pd concentration in the whole composition range. A strong Pd segregation is observed for both the orientation faces, while the amount of Pd segregation in the (I 11) face is significantly less than that in the more open (10 0) face. However, Pt segregates to the surface strongly in the Pt-Ir alloy, and the amount of Pt segregation in the (10 0) and (I 11) face is almost the same. The simulation results are in good agreement with the available experiment data and other theoretical values

Crystallization study of electroless Fe–Sn–B amorphous alloy deposits

Abstract Amorphous Fe–Sn–B alloy deposits have been first and successfully prepared by reducing iron and tin salts with KBH 4 in an aqueous solution. It was found that the deposits show an amorphous structure when the boron content ranges from 12.1 to 27.0 at.%. A two-step process of crystallization was observed for the amorphous alloys. The crystallization process of different deposits varied with the composition.

Analytic embedded-atom method approach to studying the surface segregation of Al–Mg alloys

In the present paper, the modified analytic embedded-atom method (MAEAM) many-body potentials are provided for fcc and hcp elements. The segregation energies of Mg in Al host are calculated with the MAEAM potentials. The composition depth profiles of Al–Mg alloys are obtained with Monte Carlo simulation method based on grand canonical ensemble. It is found that Mg segregates strongly to the surface layers at 600 K and the composition near the surface is monotonic to the bulk one. The simulation results are reasonable agreement with other experimental and theoretical data.