Vacancy Ordering in the Basal Plane of YB2Cu3Oz

1987 ◽  
Vol 99 ◽  
Author(s):  
L. T. Wille ◽  
A. Berera ◽  
D. De Fontaine ◽  
S. C. Moss
Keyword(s):  
Ground State ◽  
Basal Plane ◽  
Nearest Neighbors ◽  
Cluster Variation Method ◽  
Variation Method ◽  
Two Dimensional ◽  
Pairwise Interactions ◽  
Vacancy Ordering ◽  
Superconducting Compound ◽  
Cluster Variation

ABSTRACTThe ordering in the Cu-O basal plane of the high Tc superconductor YBa2Cu3Oz is investigated. Asymmetric pairwise interactions between nearest and next nearest neighbors are assumed. Ordering instabilities in two-dimensional k-space are mapped out as a function of the interactions and the ordered ground state superstructures consisting of occupied and empty oxygen sites are determined. A temperature-composition phase diagram is calculated by means of the Cluster Variation Method. The thermodynamic behavior of the superconducting compound is discussed in the light of these results.

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.

Cluster variation method for two-dimensional Hubbard and t-J models

1994 ◽  
Vol 235-240 ◽  
pp. 2187-2188 ◽  
Author(s):  
Kazunuki Tanaka ◽  
Hiromichi Ebisawa ◽  
Tohru Morita
Keyword(s):  
Cluster Variation Method ◽  
Variation Method ◽  
Two Dimensional ◽  
Cluster Variation

Order—Disorder Behavior of Grain Boundaries in a two Dimensional Mcdel Ordered Alloy

1986 ◽  
Vol 81 ◽  
Author(s):  
Diana Farkas ◽  
Ho Jang
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Pair Interaction ◽  
Cluster Variation Method ◽  
Boundary Region ◽  
Variation Method ◽  
Two Dimensional ◽  
Interaction Energies ◽  
Disordered Layer ◽  
Cluster Variation

AbstractThe order-disorder behavior of a Σ = 5 grain boundary was investigated using a two dimensional latice gas model and the cluster variation method. It is found that a disordered layer forms in the grain boundary region at temperatures significantly below theorder—disorder temperature for the bulk. Under certain assumptions for the pair interaction energies the model predicts grain boundary compositions different from the bulk.

LMTO/CVM and LAPW/CVM Calculations of the Nial-Niti Pseudobinary Phase Diagram

1990 ◽  
Vol 213 ◽  
Author(s):  
Benjamin P. Burton ◽  
Jean E. Osburn ◽  
Alain Pasturel
Keyword(s):  
Nearest Neighbor ◽  
Equations Of State ◽  
Cluster Variation Method ◽  
Variation Method ◽  
Two Phase ◽  
Pairwise Interactions ◽  
Phase Fields ◽  
Pseudobinary Phase Diagram ◽  
Total Energies ◽  
Cluster Variation

ABSTRACTLinear Muffin Tin Orbital and Linearly Augmented Plane Wave calculations of equations of state were performed for observed and hypothetical ordered structures in the NiAl-NiTi system. Total energies were parameterized in both the Connolly-Williams and ∈-G approximations, and the resulting parameters were used to calculate theoretical phase diagrams by the cluster variation method. Third nearest neighbor Al-Ti pairwise interactions are predicted to be strongly repulsive, and to be a major cause of observed B2+L21 two phase fields.

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