scholarly journals Ground State Searches in Fcc Intermetallics

1991 ◽  
Vol 253 ◽  
Author(s):  
C. Wolverton ◽  
G. Ceder ◽  
D. De Fontaine ◽  
H. Dreyssé
Keyword(s):  
Perturbation Method ◽  
Phase Diagrams ◽  
Cluster Expansion ◽  
Ground State ◽  
Nearest Neighbor ◽  
Tight Binding ◽  
Linear Constraints ◽  
Coherent Potential Approximation ◽  
Potential Approximation ◽  
Configurational Energy

ABSTRACTA cluster expansion is used to predict the fcc groutnd states, i.e., the stable phases at zero Kelvin as a function of composition, for alloy systems. TFile internetallic structures are not assumed, but derived rigorously by minimizing the configurational energy subject to linear constraints. This ground state search includes pair and multiplet interactions which spatially extend to fourth nearest neighbor. A large number of these concentration-independent interactions are computed by the method of direct configurational averaging using a linearizedmuffin- tin orbital Hamiltonian cast into tight binding form (TB-LMTO). The interactions, derived without the use of any adjustable or experimentally obtained parameters, are compared to those calculated via the generalized perturbation method extention of the coherent potential approximation within the context of a KKR Hamiltonian (KKR-CPA-GPM). Agreement with the KKR-CPA-GPM results is quite excellent, as is the comparison of the ground state results with the fcc-based portions of the experimentally-determined phase diagrams under consideration.

scholarly journals Complete catalog of ground-state diagrams for the general three-state lattice-gas model with nearest-neighbor interactions on a square lattice

2019 ◽  
Vol 21 (11) ◽  
pp. 6216-6223 ◽  
Author(s):  
Daniel Silva ◽  
Per Arne Rikvold
Keyword(s):  
Phase Diagrams ◽  
Ground State ◽  
Lattice Gas ◽  
Nearest Neighbor ◽  
Square Lattice ◽  
Temperature Phase ◽  
Zero Temperature ◽  
Dimensional Parameter ◽  
State Diagrams ◽  
Solid Foundation

The fifteen topologically different zero-temperature phase diagrams in the model's full, five-dimensional parameter space provide a solid foundation for studies at finite temperatures.

AN AUGMENTED SPACE-BASED CLUSTER COHERENT POTENTIAL APPROXIMATION: APPLICATION TO CuAu AND NiAl ALLOYS

2011 ◽  
Vol 25 (05) ◽  
pp. 735-745
Author(s):  
MOSHIOUR RAHAMAN ◽  
ABHIJIT MOOKERJEE
Keyword(s):  
Magnetic Properties ◽  
Tight Binding ◽  
Local Environment ◽  
Coherent Potential Approximation ◽  
Orbital Method ◽  
Potential Approximation ◽  
Augmented Space ◽  
Space Formalism ◽  
Random Alloys ◽  
Linear Muffin Tin Orbital

We use cluster generalization of the coherent potential approximation in the tight-binding linear muffin-tin orbital method to account for the effect of the local environment on electronic and magnetic properties of substitutional random alloys. This theory combines the augmented space formalism and conventional tight-binding linear muffin-tin orbital methods. In particular, we shall apply the technique to the bcc-based NiAl and fcc-based CuAu alloys and also compare with other approaches.

Tight-binding coherent-potential approximation including off-diagonal disorder

1989 ◽  
Vol 40 (18) ◽  
pp. 12196-12200 ◽  
Author(s):  
D. A. Papaconstantopoulos ◽  
A. Gonis ◽  
P. M. Laufer
Keyword(s):  
Tight Binding ◽  
Coherent Potential Approximation ◽  
Potential Approximation ◽  
Diagonal Disorder

A Tight-Binding Hamiltonian for the High-Temperature Superconductor YBa2Cu3O7

1988 ◽  
Vol 141 ◽  
Author(s):  
M.J. DeWeert ◽  
D.A. Papaconstantopoulos ◽  
W.E. Pickett
Keyword(s):  
Electronic Structure ◽  
High Temperature ◽  
Band Structure ◽  
Potential Application ◽  
Oxygen Vacancies ◽  
High Temperature Superconductor ◽  
Tight Binding ◽  
Coherent Potential Approximation ◽  
Potential Approximation

AbstractWe present a highly accurate tight-binding parametrization of the LAPW band structure of the high-temperature superconductor YBa2Cu3O7, discuss the methodology used in obtaining this fit, and its potential application to a Tight-Binding Coherent-Potential Approximation (TB-CPA) calculation of the effects of oxygen vacancies on the electronic structure.

Optical Properties of a Quantum Well of A1−x Bx Alloy Semiconductor in the Coherent Potential Approximation

2000 ◽  
Vol 639 ◽  
Author(s):  
Yuzo Shinozuka ◽  
Hirotsugu Kida ◽  
Masanori Watarikawa
Keyword(s):  
Optical Properties ◽  
Quantum Well ◽  
Tight Binding ◽  
Impurity Band ◽  
Coherent Potential Approximation ◽  
Electron Hole ◽  
Potential Approximation ◽  
Binding Model ◽  
Rectangular Array ◽  
One Dimensional

ABSTRACTWe have theoretically studied optical properties of a quantum well (QW) in which the well region is constructed from a binary alloy semiconductor A1−xBx in the coherent potential approximation (CPA). A tight binding model is used for a single particle (electron, hole, Frenkel exciton) in the well composed by a rectangular array of NxxNyxNz sites. The effect of the diagonal randomness is reduced to the coherent potential σ(E), which is assumed to be the same for all sites, and is selfconsistently determined with the average Green's function. For a slab (∞, ∞, Nz) and wire (∞, Ny, Nz), the density of states (E) is composed of Nz (or NyxNz) subbands, each shows the two (one)-dimensional van-Hove singularity. When x (or 1−x) is small, a B (A) impurity-band always appears at the lower (higher) energy side of the lowest (highest) host-band. The change of (E) and the absorption spectrum by changing the well-width and the dimensionality is discussed in detail.

scholarly journals Ripples in Graphene: A Variational Approach

2020 ◽  
Vol 379 (3) ◽  
pp. 915-954
Author(s):  
Manuel Friedrich ◽  
Ulisse Stefanelli
Keyword(s):  
Ground State ◽  
Energy Minimization ◽  
Variational Approach ◽  
Nearest Neighbor ◽  
Interaction Energies ◽  
Dimensional Problem ◽  
Neighbor Interaction ◽  
Configurational Energy ◽  
One Dimensional ◽  
Math Phys

Abstract Suspended graphene samples are observed to be gently rippled rather than being flat. In Friedrich et al. (Z Angew Math Phys 69:70, 2018), we have checked that this nonplanarity can be rigorously described within the classical molecular-mechanical frame of configurational-energy minimization. There, we have identified all ground-state configurations with graphene topology with respect to classes of next-to-nearest neighbor interaction energies and classified their fine nonflat geometries. In this second paper on graphene nonflatness, we refine the analysis further and prove the emergence of wave patterning. Moving within the frame of Friedrich et al. (2018), rippling formation in graphene is reduced to a two-dimensional problem for one-dimensional chains. Specifically, we show that almost minimizers of the configurational energy develop waves with specific wavelength, independently of the size of the sample. This corresponds remarkably to experiments and simulations.

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