First-Principles Study of Phase Stability in Pd-Rh Alloys

1990 ◽  
Vol 186 ◽  
Author(s):  
D.D. Johnson ◽  
P.E.A. Turchi ◽  
Marcel Sluiter ◽  
D.M. Nicholson ◽  
F.J. Pinski ◽  
...  
Keyword(s):  
Phase Separation ◽  
Phase Stability ◽  
First Principles ◽  
Ternary Addition ◽  
Potential Approximation ◽  
Effective Interactions ◽  
Reference Medium ◽  
Random Alloy ◽  
Substitutional Alloys ◽  
Effective Cluster

We present a study of the mixing energies and the effective cluster interactions which form the configurational part of the internal energy of Pd-Rh substitutional alloys. We discuss the tendency towards phase-separation and more generally phase stability. The effects of a substitutional ternary addition on the tendencies toward order or phase-separation are also reported. The Korringa-Kohn-Rostoker Coherent-Potential Approximation (KKR-CPA) is used to investigate the electronic structure effects and energetics of the random alloy. Moreover, we use the Generalized Perturbation Method (GPM), using the KKR-CPA random alloy as a reference medium, to investigate the effective interactions which determine phase stability. We briefly comment on other factors which may give important contributions to the total free-energy of the alloy. We also contrast the GPM with the Connolly-Williams approach for calculating phase diagrams from first-principles. Finally, we explore the inadequacies of the frozen-potential and Harris approximations to the energetics of alloying.

A Comparative First Principles Study of Phase Stability in Ni-Ti and Ni-Al Alloys Around Equiatomic Composition

1990 ◽  
Vol 186 ◽  
Author(s):  
P.E.A. Turchi ◽  
M. Sluiter ◽  
F.J. Pinski ◽  
D.D. Johnson
Keyword(s):  
Electronic Structure ◽  
Internal Energy ◽  
Phase Stability ◽  
First Principles ◽  
Al Alloys ◽  
Equiatomic Composition ◽  
Potential Approximation ◽  
Dependent Part ◽  
Substitutional Alloys ◽  
Effective Cluster

AbstractElectronic structure and phase stability properties of Ni-Ti and Ni-Al around equiatomic composition are investigated with a first principles approach. The study is based upon the generalized purturbation method applied to the Korringa-Kohn-Rostoker multiple scattering formulation of the coherent potential approximation. Within this framework, effective cluster interactions which build up the configuration-dependent part of the internal energy are calculated. The strength of ordering tendencies in both bcc-based substitutional alloys is compared and contrasted in terms of hybridisation effects, in relation with experimental evidences.

Electronic Structure and Phase Stability Properties of Ai-Li Alloys

1990 ◽  
Vol 186 ◽  
Author(s):  
Antonios Gonis ◽  
Patrice E.A. Turchi ◽  
Marcel Sluiter ◽  
Frank J. Pinski ◽  
Duane D. Johnson
Keyword(s):  
Phase Diagram ◽  
Electronic Structure ◽  
Perturbation Method ◽  
Multiple Scattering ◽  
Phase Stability ◽  
First Principles ◽  
Potential Approximation ◽  
Effective Interactions ◽  
Lattice Constants ◽  
Effective Cluster

AbstractRecently, the phase diagram of AI-Li alloys was calculated with the use of the Connolly-Williams method. In an effort to test the validity and to supplement the results of that study, equilibrium lattice constants and effective cluster interactions have been obtained using the generalized perturbation method within the first-principles multiple-scattering formalism of the Korringa-Kohn-Rostoker coherent-potential approximation. The implication of these effective interactions to the phase stability of these alloys is discussed.

Electronic Structure and Phase Stability Properties in Ternary Substitutional Alloys

1992 ◽  
Vol 291 ◽  
Author(s):  
Ariel J.S. Traiber ◽  
Marcel Sluiter ◽  
Patrice E.A. Turchi ◽  
Samuel M. Allen
Keyword(s):  
Electronic Structure ◽  
Tight Binding ◽  
Metal Alloys ◽  
Potential Approximation ◽  
Stability Properties ◽  
Ternary Metal ◽  
Random Alloy ◽  
Method Approach ◽  
Substitutional Alloys ◽  
Effective Cluster

ABSTRACTElectronic structure and stability properties of ternary-metal alloys are examined using an extension of the Coherent Potential Approximation -Generalized Perturbation Method approach within the Tight-Binding description of the chemically random alloy. In particular, we report on calculations of density of states, mixing energies and effective cluster interactions which build up the ordering energy. The study focuses on the Ti-V-Fe system and its binary components.

Effect of Pressure on Order and Stability in Alloys: The Case of Al-Ge

1992 ◽  
Vol 291 ◽  
Author(s):  
P. E. A. Turchi ◽  
M. Sluiter ◽  
G. M. Stocks
Keyword(s):  
Phase Separation ◽  
Phase Stability ◽  
Structural Difference ◽  
Normal Pressure ◽  
Energy Difference ◽  
Potential Approximation ◽  
Pure Species ◽  
Theoretical Predictions ◽  
Substitutional Alloys ◽  
Ordered State

ABSTRACTA parameter-free approach to phase stability in substitutional alloys is applied to the influence of pressure on order-disorder phenomena in Al-Ge. The methodology is based upon an application of the Generalized Perturbation Method to the Korringa-Kohn-Rostoker scattering formulation of the Coherent Potential Approximation. For fcc-based Al-Ge alloys, it is shown that the tendency towards phase separation at normal pressure originates from a structural difference between the pure species. By applying pressure, the structural energy difference is reduced, and a significant increase in the tendency towards order, especially for Al-rich alloys, is theoretically observed, leading, as an example, to the possible observation of a DO22 ordered state around 25 at. pct. Ge. The electronic origin of the ordering tendencies induced by pressure is discussed and the theoretical predictions are related to experimental facts.

First-principles investigations on the phase stability, elastic and thermodynamic properties of Zr–Al alloys

2015 ◽  
Vol 26 (12) ◽  
pp. 1550143 ◽  
Author(s):  
Leini Wang ◽  
Songjun Hou ◽  
Dewei Liang
Keyword(s):  
Thermodynamic Properties ◽  
Debye Temperature ◽  
Phase Stability ◽  
First Principles ◽  
Density Functional ◽  
Elastic Wave Velocity ◽  
Electronic Density ◽  
Functional Theory ◽  
High Bulk ◽  
Substitutional Alloys

In this paper, we employ first-principles methods based on electronic density functional theory (DFT) to investigate the phase stability, elastic and thermodynamic properties of Zr – Al binary substitutional alloys which are Zr 3 Al , Zr 2 Al , ZrAl , ZrAl 2 and ZrAl 3. By analyzing the elastic constants and enthalpy of formation, those phases both satisfy the generalized stability criteria and the results show that ZrAl 2 is the most stable. Due to high bulk modulus B, shear modulus G and Youngs modulus Y, ZrAl 2 also possesses excellent mechanical properties. Moreover, it is expected that there will be covalent bonding between Zr and Al atom in ZrAl 2 compound, which is confirmed by the electronic structure and the differences of charge density discussions. In the end, based on the calculated elastic modulus, the elastic wave velocity, Debye temperature ΘD and specific heat CV are discussed. As a result, ZrAl 3 possesses the highest Debye temperature and sound velocity, meaning a larger associated thermal conductivity and higher melting temperature.

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.

First-principles study of phase stability in Cu-Zn substitutional alloys

1991 ◽  
Vol 67 (13) ◽  
pp. 1779-1782 ◽  
Author(s):  
P. E. A. Turchi ◽  
M. Sluiter ◽  
F. J. Pinski ◽  
D. D. Johnson ◽  
D. M. Nicholson ◽  
...  
Keyword(s):  
Phase Stability ◽  
First Principles ◽  
First Principles Study ◽  
Substitutional Alloys

First-Principles Study of Phase Stability in Cu-Zn Substitutional Alloys

1992 ◽  
Vol 68 (3) ◽  
pp. 418-418 ◽  
Author(s):  
P. E. A. Turchi ◽  
M. Sluiter ◽  
F. J. Pinski ◽  
D. D. Johnson ◽  
D. M. Nicholson ◽  
...  
Keyword(s):  
Phase Stability ◽  
First Principles ◽  
First Principles Study ◽  
Substitutional Alloys

Ordering Mechanism in Ni-Cr Alloys: Theory and Experiment

1989 ◽  
Vol 166 ◽  
Author(s):  
P.E.A. Turchi ◽  
F.J. Pinski ◽  
R. H. Howell ◽  
A.L. Wachs ◽  
M.J. Fluss ◽  
...  
Keyword(s):  
Fermi Surface ◽  
First Principles ◽  
Alloy System ◽  
Annihilation Radiation ◽  
Potential Approximation ◽  
Flat Sheet ◽  
Inverse Monte Carlo ◽  
Atomic Interactions ◽  
Effective Cluster ◽  
Theory And Experiment

ABSTRACTRecently, short range order (SRO) parameters have been extracted from the neutron diffuse scattering intensities on Ni-Cr alloys with 11 to 25 at. pct. chromium. These data were analyzed using inverse-Monte Carlo simulations to extract atomic interactions and the results suggested the existence of a well defined, flat sheet of Fermi surface normal to the [110] direction. In this paper, this suggestion is investigated with a series of calculations which are based on the first-principles Korringa-Kohn-Rostoker-coherent-potential-approximation (KKRCPA). We calculate the electronic structure and the Bloch spectral function at the Fermi energy. We then proceed to calculate the effective cluster interactions using the generalized perturbation method (GPM) and compare them with the above-mentioned experimentally deduced interactions. In addition, we present preliminary results of two-dimensional angular correlation of positron annihilation radiation (2D-ACPAR) measurements, which probe the fermiology of this alloy system. The positron experiments demonstrate the existence of well-defined features in the Fermi surface of Ni89Cr11 but our calculations still have not yet established the origin of SRO in this system.

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.

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