Study of the Mechanical Behavior of BCC Transition Metals Using Bond-Order Potentials

1999 ◽  
Vol 578 ◽  
Author(s):  
M. Mrovec ◽  
V. Vitek ◽  
D. Nguyen-Manh ◽  
D. G. Pettifor ◽  
L. G. Wang ◽  
...  
Keyword(s):  
Transition Metals ◽  
Bond Order ◽  
Tight Binding ◽  
Dislocation Core ◽  
Body Centered Cubic ◽  
Alternative Structures ◽  
The Core ◽  
Deformation Properties ◽  
Directional Bonding ◽  
Bond Order Potentials

AbstractDeformation properties of body-centered-cubic transition metals are controlled by the core structure of screw dislocations and their studies involve extensive computer simulations. In this paper we present the recently constructed bond-order potentials (BOP) that are based on the realspace parametrized tight-binding method. In order to examine the applicability of the potentials we have evaluated the energy differences of alternative structures, investigated several transformation paths leading to large distortions and calculated phonon dispersions. Using these potentials we have calculated γ-surfaces that relate to the dislocation core structures and discuss then the importance of directional bonding in studies of dislocations in transition metals.

ANGULARLY-DEPENDENT MANY-ATOM BOND ORDER POTENTIALS WITHIN TIGHT BINDING HÜCKEL THEORY

1993 ◽  
Vol 07 (01n03) ◽  
pp. 299-304 ◽  
Author(s):  
M. AOKI ◽  
D. G. PETTIFOR
Keyword(s):  
Transition Metals ◽  
Angular Dependence ◽  
Bond Order ◽  
Tight Binding ◽  
Atomistic Simulations ◽  
Rapid Convergence ◽  
Hückel Theory ◽  
The Many ◽  
Atom Bond ◽  
Bond Order Potentials

Angularly-dependent many-atom potentials for the bond order of saturated or unsaturated bonds are derived within the tight binding (TB) Hückel approximation. These potentials are firmly based on the theorem of linearized many-atom expansion for the bond order, which is novel and gives exact bond order. The explicit angular dependence appears through the moments and interference terms about a bond. Since these potentials give an appropriate description of bonding, they should play an important role in atomistic simulations for semiconductors and transition metals and their compounds. We demonstrate the rapid convergence of the many-atom series for the potentials through some illustrative examples from s bonded elements and d bonded transition metals.

Bond-Order Potentials for Molybdenum and Niobium: An Assessment of Their Quality

1998 ◽  
Vol 538 ◽  
Author(s):  
M. Mrovec ◽  
V. Vitek ◽  
D. Nguyen-Manh ◽  
D. G. Pettifor ◽  
L. G. Wang ◽  
...  
Keyword(s):  
Bond Order ◽  
Tight Binding ◽  
Direct Calculation ◽  
Real Space ◽  
Central Force ◽  
Full Potential ◽  
Extended Defects ◽  
Many Body ◽  
Deformation Path ◽  
Bond Order Potentials

AbstractThe bond-order potentials (BOP) have been constructed for Mo and Nb. These potentials are based on the real-space parametrized tight-binding method in which diagonalization of the Hamiltonian is avoided by direct calculation of the bond-order. In this scheme the energy consists of three parts: The bond part that comprises contributions of d electrons and introduces into the scheme the covalent character of bonding, the central-force many-body part that reflects the environmental dependence of sp overlap repulsion and a pair-wise contribution. The potentials were tested by calculation of energy differences between the bcc and several alternate structures and by investigating the trigonal deformation path. These calculations have been made in parallel using BOP and the full-potential linearized augmented plane-wave method. The central-force many-body Finnis-Sinclair type potentials have also been included into the study of the deformation path. This evaluation of BOP reveals that the potentials reproduce very closely the ab initio results and are, therefore, very suitable for atomistic studies of extended defects in the transition metals.

Surface Relaxations of Aluminum Simulated by Bond Order Potentials

1999 ◽  
Vol 578 ◽  
Author(s):  
S. R. Nishitani ◽  
S. Ohgushi ◽  
H. Adachi ◽  
M. Aoki
Keyword(s):  
Bond Order ◽  
Interatomic Potential ◽  
Phonon Dispersion ◽  
Tight Binding ◽  
Dispersion Curves ◽  
Experimental Results ◽  
Phonon Dispersion Curves ◽  
Bond Order Potentials

AbstractAn interatomic potential for aluminum was developed, which is based on empirical tight binding approximations. The model successfully reproduced the shear constants, structure energy differences, and phonon dispersion curves. This transferable potential was applied on static surface relaxations, and shows good agreements with experimental results on the oscillatory damped behavior of the multilayer relaxations and the expansion of the (111) surface.

Development of Bond-Order Potentials for BCC Transition Metals

2016 ◽  
Vol 258 ◽  
pp. 3-10
Author(s):  
Vaclav Vitek ◽  
Yi Shen Lin ◽  
Matous Mrovec
Keyword(s):  
Bond Order ◽  
Phonon Dispersion ◽  
Tight Binding ◽  
Screw Dislocations ◽  
Compressive Stresses ◽  
Bcc Iron ◽  
Tight Binding Method ◽  
Formation Energies ◽  
Phonon Dispersion Relations ◽  
Bond Order Potentials

In this paper we present bond-order potentials (BOPs) based on the tight-binding method. The potentials have been developed for bcc non-magnetic metals of group V.B (V, Nb, Ta) and group VI.B (Cr, Mo, W) as well as for the ferromagnetic bcc iron. The testing of the transferability of BOPs involves energies of alternate structures, formation energies of vacancies and self-interstitials, transformation paths between different structures and phonon dispersion relations. An example of the application of these potentials is modeling of the structure and glide of 1⁄2<111> screw dislocations under the effect of applied shear and tensile/compressive stresses.

scholarly journals Bond-Order Potentials with Analytic Environment-Dependent Tight-Binding Integrals: Application to BCC Molybdenum

2000 ◽  
Vol 653 ◽  
Author(s):  
Matous Mrovec ◽  
Duc Nguyen-Manh ◽  
David G. Pettifor ◽  
Vaclav Vitek
Keyword(s):  
Bond Order ◽  
Phonon Mode ◽  
Nearest Neighbor ◽  
Tight Binding ◽  
The Core ◽  
Bcc Lattice ◽  
Binding Models ◽  
Bond Order Potential ◽  
Preliminary Study ◽  
Environmental Dependence

AbstractWe present a new Screened Bond-Order Potential (SBOP) for molybdenum in which the environmental dependence of two-center tight-binding bond integrals has been implemented via a recently developed analytic expression. These bond integrals reproduce very well the numerical ab-intio values of screened LMTO bond integrals. In particular, they display the large discontinuity in ddπ between the first and second nearest neighbor of the bcc lattice whereas they do not show any discontinuity in ddσ. This dependence can be traced directly to the angular character of the analytic screening function and is shown to be critical for the behavior of the second nearest neighbor force constants. The new BOP eliminates the problem of the very soft T2 phonon mode at the N point that is found in most two-center tight-binding models. Preliminary study of the core structure of 1/2<111> screw dislocations performed using SBOP indicates that the core is narrower and less asymmetric than structures found in previous studies, in agreement with recent ab-initio calculations.

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