Calculations of alloy phases with a direct Monte-Carlo method

Conference · Thu Sep 01 00:00:00 EDT 1994

OSTI ID:10182913

Faulkner, J S; Wang, Yang; Horvath, E A ^[1]; Stocks, G M ^[2]

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1. Florida Atlantic Univ., Boca Raton, FL (United States)
2. Oak Ridge National Lab., TN (United States)

A method for calculating the boundaries that describe solid-solid phase transformations in the phase diagrams of alloys is described. The method is first-principles in the sense that the only input is the atomic numbers of the constituents. It proceeds from the observation that the crux of the Monte-Carlo method for obtaining the equilibrium distribution of atoms in an alloy is a calculation of the energy required to replace an A atom on site i with a B atom when the configuration of the atoms on the neighboring sites, {kappa}, is specified, {delta}H{sub {kappa}}(A{yields}B) = E{sub B}{kappa} -E{sub A}{kappa}. Normally, this energy difference is obtained by introducing interatomic potentials, v{sub ij}, into an Ising Hamiltonian, but the authors calculate it using the embedded cluster method (ECM). In the ECM an A or B atom is placed at the center of a cluster of atoms with the specified configuration K, and the atoms on all the other sites in the alloy are simulated by the effective scattering matrix obtained from the coherent potential approximation. The interchange energy is calculated directly from the electronic structure of the cluster. The table of {delta}H{sub {kappa}}(A{yields}B)`s for all configurations K and several alloy concentrations is used in a Monte Carlo calculation that predicts the phase of the alloy at any temperature and concentration. The detailed shape of the miscibility gaps in the palladium-rhodium and copper-nickel alloy systems are shown.

• Research Organization: Oak Ridge National Lab., TN (United States); Florida Atlantic Univ., Boca Raton, FL (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC05-84OR21400; FG05-89ER45392
• OSTI ID: 10182913
• Report Number(s): CONF-921101-144; ON: DE94018963; TRN: 94:008557
• Resource Relation: Conference: 16. Materials Research Society (MRS) fall meeting,Boston, MA (United States),30 Nov - 5 Dec 1992; Other Information: PBD: [1994]
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
PHASE TRANSFORMATIONS
MATHEMATICAL MODELS
PALLADIUM ALLOYS
RHODIUM ALLOYS
COPPER ALLOYS
NICKEL ALLOYS
MONTE CARLO METHOD
PHASE STUDIES
PHASE DIAGRAMS
EQUILIBRIUM
ELECTRONIC STRUCTURE
360102
STRUCTURE AND PHASE STUDIES