Self-Consistent Tight-Binding Approximation Including Polarisable Ions

1997 ◽  
Vol 491 ◽  
Author(s):  
M. W. Finnis ◽  
A. T. Paxton ◽  
M. Methfesselt ◽  
M van Schilfgaarde
Keyword(s):  
Tight Binding ◽  
Structure Constant ◽  
Ceramic Materials ◽  
Fluorite Phase ◽  
Multipole Moments ◽  
Binding Model ◽  
Tight Binding Approximation ◽  
New Formalism ◽  
Self Consistent ◽  
First Time

ABSTRACTUntil recently, tight-binding has been applied to either covalent or metallic solid state systems, or charge transfer treated in a simple point charge framework. We present a self-consistent tight-binding model which, for the first time, includes electrostatic ion polar-isabihty and crystal field splitting. The tight-binding eigenvectors are used to construct multipole moments of the ionic charges which are used to obtain angular momentum components of the electrostatic potential in structure constant expansions. Our first test of the model is to study the phase stability in zirconia; in particular the instability of the fluorite phase to a spontaneous symmetry breaking, and its interpretation in terms of band effects and ion polarisability. This new formalism opens up the way to apply the tight-binding approximation to problems in which polarisation of atomic charges is important, for example oxides and other ceramic materials and surfaces of metals.

scholarly journals Cobalt-based magnetic Weyl semimetals with high-thermodynamic stabilities

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Wei Luo ◽  
Yuma Nakamura ◽  
Jinseon Park ◽  
Mina Yoon
Keyword(s):  
Tight Binding ◽  
Three Dimensional ◽  
Interlayer Coupling ◽  
First Principles Calculation ◽  
Optimization Approach ◽  
Binding Model ◽  
Nodal Lines ◽  
Weyl Semimetal ◽  
Topological Quantum ◽  
First Time

AbstractRecent experiments identified Co3Sn2S2 as the first magnetic Weyl semimetal (MWSM). Using first-principles calculation with a global optimization approach, we explore the structural stabilities and topological electronic properties of cobalt (Co)-based shandite and alloys, Co3MM’X2 (M/M’ = Ge, Sn, Pb, X = S, Se, Te), and identify stable structures with different Weyl phases. Using a tight-binding model, for the first time, we reveal that the physical origin of the nodal lines of a Co-based shandite structure is the interlayer coupling between Co atoms in different Kagome layers, while the number of Weyl points and their types are mainly governed by the interaction between Co and the metal atoms, Sn, Ge, and Pb. The Co3SnPbS2 alloy exhibits two distinguished topological phases, depending on the relative positions of the Sn and Pb atoms: a three-dimensional quantum anomalous Hall metal, and a MWSM phase with anomalous Hall conductivity (~1290 Ω−1 cm−1) that is larger than that of Co2Sn2S2. Our work reveals the physical mechanism of the origination of Weyl fermions in Co-based shandite structures and proposes topological quantum states with high thermal stability.

scholarly journals Single-crystalline epitaxial TiO film: A metal and superconductor, similar to Ti metal

2021 ◽  
Vol 7 (2) ◽  
pp. eabd4248
Author(s):  
Fengmiao Li ◽  
Yuting Zou ◽  
Myung-Geun Han ◽  
Kateryna Foyevtsova ◽  
Hyungki Shin ◽  
...  
Keyword(s):  
Transition Metal ◽  
Density Functional ◽  
Tight Binding ◽  
Crystal Form ◽  
Titanium Monoxide ◽  
Binding Model ◽  
Functional Theory ◽  
Single Crystalline ◽  
First Time ◽  
Lattice Matched

Titanium monoxide (TiO), an important member of the rock salt 3d transition-metal monoxides, has not been studied in the stoichiometric single-crystal form. It has been challenging to prepare stoichiometric TiO due to the highly reactive Ti2+. We adapt a closely lattice-matched MgO(001) substrate and report the successful growth of single-crystalline TiO(001) film using molecular beam epitaxy. This enables a first-time study of stoichiometric TiO thin films, showing that TiO is metal but in proximity to Mott insulating state. We observe a transition to the superconducting phase below 0.5 K close to that of Ti metal. Density functional theory (DFT) and a DFT-based tight-binding model demonstrate the extreme importance of direct Ti–Ti bonding in TiO, suggesting that similar superconductivity exists in TiO and Ti metal. Our work introduces the new concept that TiO behaves more similar to its metal counterpart, distinguishing it from other 3d transition-metal monoxides.

Self-consistent tight binding model adapted for hydrocarbon systems

2005 ◽  
Vol 31 (8) ◽  
pp. 585-595 ◽  
Author(s):  
D. A. Areshkin ◽  
O. A. Shenderova ◽  
J. D. Schall ◽  
D. W. Brenner
Keyword(s):  
Tight Binding ◽  
Tight Binding Model ◽  
Binding Model ◽  
Self Consistent

The Atomic and Electronic Structures of Grain Boundaries in Silicon-Carbide and Silicon

1990 ◽  
Vol 193 ◽  
Author(s):  
M. Kohyama ◽  
S. Kose ◽  
M. Kinoshita ◽  
R. Yamamoto
Keyword(s):  
Electronic Structure ◽  
Electronic Structures ◽  
Boundary Energy ◽  
Tight Binding ◽  
Atomic Model ◽  
Electrostatic Energy ◽  
Hrem Image ◽  
Self Consistent ◽  
First Time ◽  
Atomic And Electronic Structure

ABSTRACTThe atomic and electronic structure of the {122} Σ=9 grain boundary in cubic SiC has been calculated for the first time using the self-consistent tight-binding (SCTB) method. An atomic model consisting of zigzag arrangement of 5-membered and 7-membered rings similar to that in the same boundary in Si or Ge has been constructed from a HREM image, although Si-Si and C-C wrong bonds are repeated alternately at the interface in this model. We have also performed calculations of the same boundary in Si using the SCTB method for comparison, and have obtained the results similar to those previously obtained by other theoretical schemes. The calculated boundary energy in SiC has shown that the present atomic model can exist stably as compared with the two surfaces, and the calculated boundary electronic structure in SiC has no deep states in the gap as well as that in Si. However, it has been found that the the increase in the electrostatic energy caused by the wrong bonds is a large part of the present boundary energy in SiC differently from that in Si, and it has been shown that the wrong bonds introduce the wrong-bond localised states at the band edges and within the valence band.

scholarly journals Intrinsic Spin-Orbit Coupling in Zigzag and Armchair Graphene Nanoribbons

2011 ◽  
Vol 2011 ◽  
pp. 1-7
Author(s):  
Ying Li ◽  
Erhu Zhang ◽  
Baihua Gong ◽  
Shengli Zhang
Keyword(s):  
Graphene Nanoribbons ◽  
Tight Binding ◽  
Geometrical Parameters ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Binding Model ◽  
Tight Binding Approximation ◽  
Energy Gaps ◽  
Armchair Graphene Nanoribbons ◽  
Armchair Graphene

Starting from a tight-binding model, we derive the energy gaps induced by intrinsic spin-orbit (ISO) coupling in the low-energy band structures of graphene nanoribbons. The armchair graphene nanoribbons may be either semiconducting or metallic, depending on their widths in the absence of ISO interactions. For the metallic ones, the gaps induced by ISO coupling decrease with increasing ribbon widths. For the ISO interactions, we find that zigzag graphene nanoribbons with odd chains still have no band gaps while those with even chains have gaps with a monotonic decreasing dependence on the widths. First-principles calculations have also been carried out, verifying the results of the tight-binding approximation. Our paper reveals that the ISO interaction of graphene nanoribbons is governed by their geometrical parameters.

Dynamics of the Formation of the Nitrogen-Vacancy Center in Diamond

2016 ◽  
Vol 19 (2) ◽  
pp. 380-392 ◽  
Author(s):  
Amihai Silverman ◽  
Joan Adler ◽  
Rafi Kalish
Keyword(s):  
Density Functional ◽  
Tight Binding ◽  
Interstitial Site ◽  
Nitrogen Vacancy ◽  
Tight Binding Approximation ◽  
Substitutional Site ◽  
Nitrogen Vacancy Center ◽  
Self Consistent ◽  
Nv Center ◽  
Vacancy Center

AbstractWe present results of simulations of the energetics and dynamics involved in the realization of the NV (nitrogen-vacancy) center in diamond. We use the self-consistent charge-density functional tight-binding approximation and show that when the nitrogen resides on a single substitutional site, it fails to attract a vacancy, hence no NV center can be formed. However, if it occupies a split interstitial site and two vacancies reside on the second or third neighbor sites, an NV center will form following annealing at temperatures as low as 300°C and 650°C, respectively. These results provide guidelines to experimentalists on how to increase the efficiency of NV formation in diamond.

scholarly journals Influence of Internal Electric Fields on the Ground Level Emission of GaN/AlGaN Multi-Quantum Wells

2000 ◽  
Vol 5 (S1) ◽  
pp. 970-976
Author(s):  
A. Bonfiglio ◽  
M. Lomascolo ◽  
G. Traetta ◽  
R. Cingolani ◽  
A. Di Carlo ◽  
...  
Keyword(s):  
Experimental Data ◽  
Quantum Wells ◽  
Electric Fields ◽  
Tight Binding ◽  
Ground Level ◽  
Analytic Model ◽  
Tight Binding Model ◽  
Binding Model ◽  
Emission Energy ◽  
Self Consistent

The spectroscopic investigation of GaN/AlGaN quantum wells reveals that the emission energy of such structures is determined by four parameters, namely composition, well-width, strain and charge density. The experimental data obtained by varying these parameters are quantitatively explained by an analytic model based on the envelope function formalism which accounts for screening and built-in field, and by a full self-consistent tight-binding model.

Influence of Internal Electric Fields on the Ground Level Emission of GaN/AlGaN Multi-Quantum Wells

1999 ◽  
Vol 595 ◽  
Author(s):  
A. Bonfiglio ◽  
M. Lomascolo ◽  
G. Traetta ◽  
R. Cingolani ◽  
A. Di Carlo ◽  
...  
Keyword(s):  
Experimental Data ◽  
Quantum Wells ◽  
Electric Fields ◽  
Tight Binding ◽  
Ground Level ◽  
Analytic Model ◽  
Tight Binding Model ◽  
Binding Model ◽  
Emission Energy ◽  
Self Consistent

AbstractThe spectroscopic investigation of GaN/AlGaN quantum wells reveals that the emission energy of such structures is determined by four parameters, namely composition, well-width, strain and charge density. The experimental data obtained by varying these parameters are quantitatively explained by an analytic model based on the envelope function formalism which accounts for screening and built-in field, and by a full self-consistent tight-binding model.

Sign in / Sign up

Export Citation Format

Share Document