Identification of novel diffusion cycles in B2 ordered phases by Monte Carlo simulation

Abstract Atomic migration in ordered binary alloys with B2 structure is studied by atomistic Monte Carlo simulations where atom migration results from exchanges with a single vacancy on a rigid lattice. Highly correlated vacancy sequences are observed and studied using improved residence time algorithms. It is shown that, for partially ordered structures, the classical six-jump cycles contribute only partially to the diffusion process, and that a wide range of other correlated sequences are observed, including the recently proposed antisite bridge mechanism. Among the other sequences, we have identified six-jump cycles that are assisted by antisites. Furthermore, when atomic interaction energies present a high degree of asymmetry, two effects have been observed: the ratio of tracer diffusion coefficients increases as a result of additional loops involved in the six-jump cycles; diffusion coefficients exhibit an upward curvature below the order-disorder transition temperature. These two effects have been o...

[1]  G. Murch,et al.  Computer simulation of tracer diffusion in a binary ordered alloy with an equilibrium concentration of vacancies , 1993 .

[2]  I. Belova,et al.  Diffusion in a model of an ordered alloy , 1995 .

[3]  D. Srolovitz,et al.  Determination of vacancy and atomic diffusivities in solid solution alloys , 1996 .

[4]  N. Stolwijk,et al.  Self-diffusion in the intermetallic compound CoGa , 1980 .

[5]  R. Kikuchi,et al.  Tetrahedron approximation of the cluster variation method for b.c.c. alloys , 1989 .

[6]  G. Murch.  Diffusion in solids unsolved problems , 1992 .

[7]  M. Novotny,et al.  A new approach to an old algorithm for the simulation of Ising-like systems , 1995 .

[8]  S. M. Kim.  Vacancy properties in ordered CoGa and FeAl , 1988 .

[9]  B. Sepiol,et al.  Elementary diffusion jump of iron atoms in intermetallic phases studied by Mössbauer spectroscopy—I. FeAl close to equiatomic stoichiometry , 1994 .

[10]  A. B. Bortz,et al.  A new algorithm for Monte Carlo simulation of Ising spin systems , 1975 .

[11]  C. Elsässer,et al.  Concentrations of Atomic Defects in B2FexAl1−x. An Ab-Initio Study , 1995 .

[12]  Frédéric Soisson,et al.  Monte Carlo simulations of copper precipitation in dilute iron-copper alloys during thermal ageing and under electron irradiation , 1996 .

[13]  Martin,et al.  Atomic mobility in Cahn's diffusion model. , 1990, Physical review. B, Condensed matter.

[14]  Fu Cl.  Origin of ordering in B2-type transition-metal aluminides: Comparative study of the defect properties of PdAl, NiAl, and FeAl. , 1995 .

[15]  R. Kikuchi,et al.  Substitutional Diffusion in an Ordered System , 1969 .

[16]  W. A. Oates,et al.  Configurational thermodynamics of vacancy formation in solids by Monte Carlo simulation , 1992 .

[17]  Ye,et al.  Equilibrium point defects in intermetallics with the B2 structure: NiAl and FeAl. , 1993, Physical review. B, Condensed matter.

[18]  W M Young,et al.  Monte Carlo studies of vacancy migration in binary ordered alloys: I , 1966 .

[19]  C. Mccombie,et al.  Vacancy Diffusion in Binary Ordered Alloys , 1958 .

[20]  M. Koiwa,et al.  Diffusion mechanisms in ordered alloys—a detailed analysis of six-jump vacancy cycle in the B2 type lattice , 1989 .

[21]  J. P. Neumann,et al.  Thermodynamics of intermetallic phases with the triple-defect B2 structure , 1976 .

[22]  Limoge,et al.  Temperature behavior of tracer diffusion in amorphous materials: A random-walk approach. , 1990, Physical review letters.

[23]  C. Kao,et al.  On the composition dependencies of self-diffusion coefficients in B2 intermetallic compounds , 1993 .

[24]  M. Athènes,et al.  A Monte-Carlo study of B2 ordering and precipitation via vacancy mechanism in b.c.c. lattices , 1996 .