Tight-Binding Lmto Approach to the Electronic Structure and Atomic Configuration in Extended Defects in Metals

1992 ◽  
Vol 278 ◽  
Author(s):  
M. ŠOB ◽  
V. Vitek ◽  
Y. Oh
Keyword(s):  
Total Energy ◽  
Tight Binding ◽  
Pair Potential ◽  
Quantum Mechanical ◽  
Orbital Method ◽  
Extended Defects ◽  
Many Body ◽  
Quantum Mechanical Treatment ◽  
Quantum Mechanical Method ◽  
Sphere Approximation

AbstractA new quantum-mechanical method capable of determining atomic configurations of extended defects has been developed. The Hamiltonian is constructed using the first-principles tight-binding linear muffin-tin orbital method in the atomic-sphere approximation. A semiempirical correction is employed to describe the effect of electrons in the interstitial region and the repulsive part of the total energy is described by a pair potential. The forces on atoms are calculated by differentiating the corresponding energy terms with respect to atomic positions. The equilibriun configuration is then found by minimizing the total energy. In this approach, the electronic and chemical aspects of defect structures can be accounted for more adequately than when using central-force pair or many-body potentials. In particular, the angular dependence of interatomic forces, which is important in transition metals with unfilled d-bands, is described correctly within the present quantum-mechanical treatment.

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.

Semi-Empirical Tight-Binding Parameters for Total Energy Calculation in Zinc

1997 ◽  
Vol 491 ◽  
Author(s):  
A. Bere ◽  
A. Hairie ◽  
G. Nouet ◽  
E. Paumier
Keyword(s):  
Total Energy ◽  
Interatomic Potential ◽  
Tight Binding ◽  
Energy Calculation ◽  
Extended Defects ◽  
Binding Parameters ◽  
Total Energy Calculation ◽  
Tight Binding Method ◽  
The Stability ◽  
Semi Empirical

ABSTRACTThe semi-empirical tight-binding method is used to build up an interatomic potential in zinc. Using relaxed structures, the parameters are fitted to the lattice parameters, the elastic constants and the vacancy formation energy. The total energy calculation predicts the stability of the h.c.p. structure. The potential is used to calculate the energy of some extended defects: the basal stacking fault and two twin boundaries.

La3Ni4Al2: a new layered aluminide

2019 ◽  
Vol 234 (9) ◽  
pp. 581-586
Author(s):  
Nazar Zaremba ◽  
Yurij Schepilov ◽  
Galyna Nychyporuk ◽  
Viktor Hlukhyy ◽  
Volodymyr Pavlyuk
Keyword(s):  
Crystal Structure ◽  
Tight Binding ◽  
Orbital Method ◽  
Single Crystal Diffraction ◽  
Coordination Polyhedra ◽  
Atomic Sphere ◽  
X Ray ◽  
Square Prism ◽  
Sphere Approximation ◽  
Structure Calculations

Abstract The new ternary compound La3Ni4Al2 has been synthesized and the crystal structure has been studied by X-ray single crystal diffraction. La3Ni4Al2 is the first aluminide, crystallizing in the La3Ni4Ga2-type. The crystal structure of La3Ni4Al2 consists of La-layers and hetero-atomic Ni/Al layers, sequentially alternating along the a axis (pseudo-hexagonal c axis). According to electronic structure calculations using the tight-binding linear muffin-tin orbital method in the atomic-sphere approximation (TB-LMTO-ASA), strong Al–Ni interactions have been established. The coordination polyhedra for the Al atoms are cuboctahedra, whereas the bicapped square prism and bicapped square antiprism are typical for nickel atoms. The lanthanum atoms are enclosed in pseudo Frank–Kasper polyhedra.

Electronic Structure and Energetics of LaNi5, α-La2Ni10H and β-La2Ni10H14

1998 ◽  
Vol 513 ◽  
Author(s):  
H. Nakamura ◽  
D. Nguyen-Manh ◽  
D. G. Pettifor
Keyword(s):  
Electronic Structure ◽  
Total Energy ◽  
Charge Density ◽  
Tight Binding ◽  
Site Occupancy ◽  
Heat Of Formation ◽  
Hydrogen Atoms ◽  
Atomic Sphere ◽  
Sphere Approximation ◽  
Atomic Sphere Approximation

ABSTRACTThe electronic structure and energetics of LaNi5, its hydrogen solution (α-La2Ni10H) and its hydride (β-La2Ni10H14) were investigated by means of the tight-binding linear muffin-tin orbitals method within the atomic sphere approximation (TB-LMTO-ASA). Preferred site occupancy by the absorbed hydrogen atoms was investigated in terms of the charge density of the interstitial sites and the total energy, both of which indicate that the 6m site in the P6/mmm symmetry is the most preferred. A negative heat of formation of La2Ni10H14 was obtained from the total energy calculations.

scholarly journals Quantum mechanics of proteins in explicit water: The role of plasmon-like solute-solvent interactions

2019 ◽  
Vol 5 (12) ◽  
pp. eaax0024 ◽  
Author(s):  
Martin Stöhr ◽  
Alexandre Tkatchenko
Keyword(s):  
Density Functional ◽  
Van Der Waals ◽  
Tight Binding ◽  
Quantum Mechanical ◽  
Dispersion Interactions ◽  
Many Body ◽  
Biomolecular Systems ◽  
Range Interaction ◽  
Factors Affecting ◽  
Quantum Mechanical Approach

Quantum-mechanical van der Waals dispersion interactions play an essential role in intraprotein and protein-water interactions—the two main factors affecting the structure and dynamics of proteins in water. Typically, these interactions are only treated phenomenologically, via pairwise potential terms in classical force fields. Here, we use an explicit quantum-mechanical approach of density-functional tight-binding combined with the many-body dispersion formalism and demonstrate the relevance of many-body van der Waals forces both to protein energetics and to protein-water interactions. In contrast to commonly used pairwise approaches, many-body effects substantially decrease the relative stability of native states in the absence of water. Upon solvation, the protein-water dispersion interaction counteracts this effect and stabilizes native conformations and transition states. These observations arise from the highly delocalized and collective character of the interactions, suggesting a remarkable persistence of electron correlation through aqueous environments and providing the basis for long-range interaction mechanisms in biomolecular systems.

Electronic Structure and Atomic Configuration of Extended Defects in Metals by First-Principles and Semiempirical TB-LMTO Methods

1997 ◽  
Vol 491 ◽  
Author(s):  
M. Šob ◽  
I. Turek ◽  
V. Vitek
Keyword(s):  
Electronic Structure ◽  
First Principles ◽  
Magnetic Moments ◽  
Tight Binding ◽  
Local Environment ◽  
Ground State Structure ◽  
Full Potential ◽  
Extended Defects ◽  
Semiempirical Approach ◽  
Sphere Approximation

ABSTRACTWe present two tight-binding linear muffin-tin orbitals (TB-LMTO) techniques for electronic structure calculations of extended defects (such as grain boundaries, interphase interfaces, surface layers etc.) in metals. The first is based on the first-principles self-consistent surface Green's function approach within the atomic-sphere approximation (ASA) utilizing two-dimensional periodicity in the layers parallel to the interface. In the second approach the Hamiltonian is constructed within the TB-LMTO-ASA as well, but semiempirical terms are employed to characterize the repulsive part of the interaction and the effect of electrons in interstitial space. While the adjustable parameters have only been fitted to the properties of ideal ground state structure, the semiempirical approach describes correctly the structural energy differences, phonon frequencies etc. Two examples are presented: the electronic structure of the Σ = 5(210)/[001] tilt grain boundary in tungsten is determined and the sensitivity of 4d magnetic moments in thin films to local environment is discussed. A comparison of the semiempirical TB-LMTO-ASA with the first-principles full-potential LMTO results is performed along the trigonal deformation path connecting the bcc, simple cubic and fee structures and the applicability of the semiempirical approach for simulating atomic structure of extended defects is assessed.

Some U(n1 + n2) ⊃U(n1) ⊗U(n2) isoscalar factors

2017 ◽  
Vol 26 (09) ◽  
pp. 1750057 ◽  
Author(s):  
H. G. Ganev
Keyword(s):  
Mechanical Treatment ◽  
Quantum Mechanical ◽  
Many Body ◽  
Type Formula ◽  
Quantum Mechanical Treatment ◽  
Two Component ◽  
Many Body Systems

Some of the [Formula: see text] isoscalar factors (IFs), involving the [Formula: see text] couplings of the type [Formula: see text], are obtained using the building-up procedure. It is shown that such type of IFs are relevant to the quantum-mechanical treatment of the two-component many-body systems.

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