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.

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.

Tight-binding bond order potential a forces for atomistic simulations

1997 ◽  
Vol 18 (6) ◽  
pp. 614-623 ◽  
Author(s):  
M. Aoki ◽  
A. P. Horsfield ◽  
D. G. Pettifor
Keyword(s):  
Bond Order ◽  
Tight Binding ◽  
Atomistic Simulations ◽  
Bond Order Potential

scholarly journals BOPfox program for tight-binding and analytic bond-order potential calculations

2019 ◽  
Vol 235 ◽  
pp. 221-233 ◽  
Author(s):  
T. Hammerschmidt ◽  
B. Seiser ◽  
M.E. Ford ◽  
A.N. Ladines ◽  
S. Schreiber ◽  
...  
Keyword(s):  
Bond Order ◽  
Tight Binding ◽  
Bond Order Potential

scholarly journals A Combined Ab Initio and Bond-Order Potentials Study of Cohesion in Iridium

2003 ◽  
Vol 779 ◽  
Author(s):  
Marc J. Cawkwell ◽  
Duc Nguyen-Manh ◽  
Vaclav Vitek ◽  
David G. Pettifor
Keyword(s):  
Ab Initio ◽  
Bond Order ◽  
Tight Binding ◽  
Full Potential ◽  
Extended Defects ◽  
Cauchy Pressure ◽  
Deformation And Fracture ◽  
Phonon Spectra ◽  
Resistance To Oxidation ◽  
Bond Order Potential

AbstractThe extremely high melting point and excellent resistance to oxidation and corrosion offered by iridium suggest numerous applications of this transition metal in static components at high temperatures and in aggressive environments. However, the mechanical and physical properties of f.c.c. Ir exhibit numerous anomalies when compared to other metals that crystallize in the f.c.c. structure. Notable examples include a negative Cauchy pressure, 1/2 (C12 – C44), brittle transgranular cleavage after a period of plastic flow even in pure single crystals and anomalous [ΆΆ0] branches in the phonon spectra. Atomistic studies of extended defects are needed to elucidate the origin of anomalous mechanical properties, such as brittleness. For this purpose we developed a Bond-Order Potential (BOP), an O(N) tight-binding formalism, employing physically transparent parameterizations that use experimental and ab initio data, generated in this study using the Full Potential Augmented Plane Wave plus Local Orbitals (APW+lo) method. The constructed BOP reproduces then both equilibrium as well as a variety of nonequilibrium properties of Ir and represents an excellent description of cohesion in f.c.c. Ir. This description of interatomic interactions is imminently suitable for studies of defects, such as dislocations and grain boundaries, that control plastic deformation and fracture.

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