Real Space Multiple Scattering Description of Alloy Phase Stability

1991 ◽  
Vol 253 ◽  
Author(s):  
P. E. A. Turchi ◽  
M. Sluiter
Keyword(s):  
Multiple Scattering ◽  
Phase Stability ◽  
Antiphase Boundary ◽  
Cluster Variation Method ◽  
Real Space ◽  
Variation Method ◽  
Study Phase ◽  
Interfacial Energies ◽  
Cluster Variation ◽  
The Stability

ABSTRACTWe present a brief overview of the advanced methodology which has been recently developed to study phase stability properties of substitutional alloys, including order-disorder phenomena and structural transformations. The approach is based on the real space version of the Generalized Perturbation Method, first introduced by Ducastelle and Gautier, within the Korringa-Kohn- Rostoker multiple scattering formulation of the Coherent Potential Approximation. Temperature effects are taken into account with a generalized meanfield approach, namely the Cluster Variation Method. The viability and the predictive power of such a scheme will be illustrated by a few examples, among them: (1) the ground state properties of alloys, in particular the ordering tendencies for a series of equiatomic bcc-based alloys, (2) the computation of alloy phase diagrams with the case of fcc and bcc-based Ni-Al alloys, (3) the calculation of antiphase boundary energies and interfacial energies, and (4) the stability of artificial ordered superlattices.

A First Principles Examination of Phase Stability in Fcc-Based Ni-V Substitutional Alloys

1990 ◽  
Vol 186 ◽  
Author(s):  
J. Mikalopas ◽  
P.E.A. Turchi ◽  
M. Sluiter ◽  
P.A. Sterne
Keyword(s):  
Phase Stability ◽  
Ground State ◽  
First Principles ◽  
Cluster Variation Method ◽  
Variation Method ◽  
Many Body ◽  
Cluster Variation ◽  
Many Body Interactions ◽  
Ground State Energies ◽  
Substitutional Alloys

AbstractThe phase stability of fcc-based Ni-V substitutional alloys is investigated using linear muffin-tin orbitals total energy (LMTO) calculations. The method of Connolly and Williams (CWM) is used to extract many body interactions from the ground state energies of selected ordered configurations. These interactions are used in conjunction with the cluster variation method (CVM) to calculate the alloy phase diagram. The dependence of the interactions on the choice of configurations used to calculate them is examined.

scholarly journals First-Principles Study of Intermetallic Phase Stability in the Ternary Ti-Al-Nb Alloy System

1994 ◽  
Vol 364 ◽  
Author(s):  
Mark Asta ◽  
Alim Ormeci ◽  
John M. Wills ◽  
Robert C. Albers
Keyword(s):  
First Principles ◽  
Intermetallic Phase ◽  
Alloy System ◽  
Cluster Variation Method ◽  
Ternary Alloys ◽  
Interaction Parameters ◽  
Variation Method ◽  
Cluster Variation ◽  
The Stability ◽  
Alloy Thermodynamic

AbstractThe stability of bcc-based phases in the Ti-Al-Nb alloy system has been studied from first-principles using a combination of ab-initio total energy and cluster variation method (CVM) calculations. Total energies have been computed for 18 binary and ternary bcc superstructures in order to determine low temperature ordering tendencies. From the results of these calculations a set of effective cluster interaction parameters have been derived. These interaction parameters are required input for CVM computations of alloy thermodynamic properties. The CVM has been used to study the effect of composition on finite-temperature ordering tendencies and site preferences for bcc-based phases. Strong ordering tendencies are observed for binary Nb-Al and Ti-Al bcc phases as well as for ternary alloys with compositions near Ti2AlNb. For selected superstructures we have also analyzed structural stabilities with respect to tetragonal distortions which transform the bcc into an fcc lattice. Instabilities with respect to such distortions are found to exist for binary but not ternary bcc compounds.

scholarly journals A First-Principles Study of the Phase Stability of FCC-Based Ti-Al Alloys

1992 ◽  
Vol 278 ◽  
Author(s):  
Mark Asta ◽  
Didier De Fontaine ◽  
Mark Van Schilfgaarde ◽  
Marcel Sluiter ◽  
Michael Methfessel
Keyword(s):  
Phase Stability ◽  
First Principles ◽  
Cluster Variation Method ◽  
Stability Study ◽  
Al Alloys ◽  
Variation Method ◽  
Orbital Method ◽  
Temperature Phase ◽  
Full Potential ◽  
Cluster Variation

AbstractIn this paper we present results of a first-principles phase stability study of fcc-based Ti-Al alloys. In particular, the full-potential linear muffin tin orbital method has been used to determine heats of formation and other zero-temperature properties of 9 fcc ordered superstructures as well as fcc and hcp Ti, and fcc Al. From these results a set of effective cluster interactions are determined which are used in a cluster variation method calculation of the thermodynamic properties and the composition-temperature phase diagram of fcc-based alloys.

First-principles study of phase stability of Ti–Al intermetallic compounds

1993 ◽  
Vol 8 (10) ◽  
pp. 2554-2568 ◽  
Author(s):  
Mark Asta ◽  
Didier de Fontaine ◽  
Mark van Schilfgaarde
Keyword(s):  
Intermetallic Compounds ◽  
Phase Stability ◽  
First Principles ◽  
Experimental Studies ◽  
Cluster Variation Method ◽  
Variation Method ◽  
Orbital Method ◽  
Temperature Phase ◽  
Full Potential ◽  
Cluster Variation

Thermodynamic and structural properties of fcc- and hcp-based Ti–Al alloys are calculated from first-principles and are used to perform an ab initio study of phase stability for the intermetallic compounds in this system. The full potential linear muffin tin orbital method is used to determine heats of formation and other zero-temperature properties of 9 fcc- and 7 hcp-based intermetallic compounds, as well as of elemental fcc and hcp Ti and Al. From the results of these calculations, sets of effective cluster interactions are derived and are used in a cluster variation method calculation of the solid-state portion of the composition-temperature phase diagram for fcc- and hcp-based alloy phases. The results of our calculations are compared with those of experimental studies of stable and metastable phases in the Ti–Al system.

SHORT RANGE ORDERING AND LOCAL DISPLACEMENT OF ALLOYS STUDIED BY CVM

2012 ◽  
Vol 01 (02) ◽  
pp. 1250018 ◽  
Author(s):  
TETSUO MOHRI
Keyword(s):  
Short Range ◽  
Lattice Distortion ◽  
Cluster Variation Method ◽  
Real Space ◽  
Variation Method ◽  
Diffuse Intensity ◽  
Local Lattice Distortion ◽  
Wide Range ◽  
Local Lattice ◽  
Cluster Variation

Cluster Variation Method (CVM) is a powerful statistical mechanics means to investigate phase equilibria of an alloy. The advantageous feature of the CVM stems from the fact that wide range of atomic correlations which play an important role at the phase transition is efficiently incorporated into the free energy formula. Hence, configurational fluctuation can be systematically studied through the calculations of correlation functions in the real space and short range order diffuse intensity spectrum in the k-space. However, one of the deficiencies of the conventional CVM is the fact that local lattice distortion (local atomic displacement) is not correctly dealt with. In order to improve such shortcomings, Continuous Displacement Cluster Variation Method (CDCVM) has been developed. In the CDCVM, local lattice distortion is mapped onto the configurational freedom of a multi-component alloy on a rigid (uniformly deformable) lattice. With CDCVM, the applicability of CVM is enlarged and the calculations of diffuse intensity spectrum originating from local lattice distortion can be performed.

scholarly journals Ab-Initio Calculations for Solvus Temperatures of Pd-Rich PdRu Alloys: Real-Space Cluster Expansion and Cluster Variation Method

2018 ◽  
Vol 59 (3) ◽  
pp. 338-347 ◽  
Author(s):  
Chang Liu ◽  
Mitsuhiro Asato ◽  
Nobuhisa Fujima ◽  
Toshiharu Hoshino ◽  
Ying Chen ◽  
...  
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Cluster Expansion ◽  
Cluster Variation Method ◽  
Real Space ◽  
Variation Method ◽  
Cluster Variation

Theoretical Investigation of Fe-Based Phase Equilibria from the First-Principles

2005 ◽  
Vol 475-479 ◽  
pp. 3127-3130 ◽  
Author(s):  
Ying Chen ◽  
Shuichi Iwata ◽  
Tetsuo Mohri
Keyword(s):  
Theoretical Investigation ◽  
Phase Stability ◽  
First Principles ◽  
Cluster Variation Method ◽  
High Accuracy ◽  
Variation Method ◽  
Transition Temperatures ◽  
Spin Polarized ◽  
Cluster Variation ◽  
Effective Cluster

Theoretical investigation of the phase equilibira of three kinds of Fe-based alloys, Fe-Ni, Fe-Pd and Fe-Pt systems is attempted by combining FLAPW total energy calculations and Cluster Variation Method. It is revealed that the magnetism plays a crucial role in the phase stability and spin polarized calculation is indispensable. The experimental L10-disorder transition temperatures are reproduced with fairly high accuracy. Thermal vibration effects incorporated based on the Debye-Gruneisen model further improve the calculated transition temperatures. Furthermore, the influence of the various effective cluster interactions on phase stability is calculated systematically.

Modeling of Antiphase Boundaries in L12 Structures

1986 ◽  
Vol 81 ◽  
Author(s):  
J.M. Sanchez ◽  
S. Eng ◽  
Y.P. Wu ◽  
J.K. Tien
Keyword(s):  
Antiphase Boundary ◽  
Cluster Variation Method ◽  
Variation Method ◽  
Bulk Alloy ◽  
Antiphase Boundaries ◽  
Ordered Structures ◽  
Wetting Transitions ◽  
Ordered Alloys ◽  
Disordered Layer ◽  
Cluster Variation

AbstractThe thermodynamic properties of conservative (111) antiphase boundaries in L12 ordered structures are modeled using the tetrahedron approximation of the cluster variation method. The concentration and long-range order parameter profiles are determined as a function of temperature and composition of the bulk alloy. Characteristic wetting transitions, with a macroscopic disordered layer growing from the antiphase boundary as the transition temperature is approached, are found for all cases investigated. The effectof antiphase boundaries on the disordering of ordered alloys and on the gliding of superdislocations are discussed.

First-principle Thoery of Phase Stability, Phase Equilibria and Phase Transition of Ordered Compounds

2006 ◽  
Vol 980 ◽  
Author(s):  
Tetsuo Mohri
Keyword(s):  
Electronic Structure ◽  
First Principles ◽  
Future Prospect ◽  
Cluster Variation Method ◽  
First Principles Calculation ◽  
Variation Method ◽  
Cluster Variation ◽  
The Stability ◽  
Noble Metal Alloys ◽  
Alloy Systems

AbstractFirst-principles theory of alloys is based on electronic structure calculation at the ground state and statistical mechanics calculation at finite temperatures. The former clarifies the stability of an ordered compound against competing phases and the latter is employed mainly to derive a phase diagram. The author performed a series of first-principles investigations on binary alloy systems including noble metal alloys, semiconductor alloys and Fe-based alloy systems by combining FLAPW electronic structure total energy calculations with Cluster Variation Method. Recently, the theoretical framework is extended even to calculate microstructural evolution process. By exemplifying Fe-based alloy systems, the progress of the first-principles calculation is reviewed and future prospect is discussed.

Application of Continuous Displacement Cluster Variation Method to Study Phase Equilibria

2010 ◽  
Vol 654-656 ◽  
pp. 1496-1499
Author(s):  
Tetsuo Mohri
Keyword(s):  
Transition Temperature ◽  
Phase Equilibria ◽  
Lattice Distortion ◽  
Cluster Variation Method ◽  
Variation Method ◽  
Study Phase ◽  
Local Lattice Distortion ◽  
Local Lattice ◽  
Cluster Variation ◽  
Continuous Displacement

Cluster Variation Method (CVM) has been widely recognized as one of the most reliable theoretical tools to study phase equilibria in metallic alloy systems. The conventional CVM, however, does not allow atomic local displacements and, therefore, calculated results often encounter various inconveniences such as the overestimation of transition temperatures. Continuous Displacement Cluster Variation Method (CDCVM) was proposed to circumvent such deficiencies of the conventional CVM. Preliminary studies on an order-disorder phase diagram based on CDCVM indicate that the transition temperature is shifted downward reproducing experimental tendencies. In the present study, lattice thermal vibration effects are also incorporated through Morse potential. It is concluded that the local lattice distortion effects are quite effective to reduce the transition temperature.

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