A semi-empirical tight-binding calculation of the band structure of MoS2

<div>Ultra-thin body (UTB) devices are being used in many electronic applications operating over a wide range of temperatures. The electrostatics of these devices depends on the band structure of the channel material, which varies with temperature as well as channel thickness. The semi-empirical tight binding (TB) approach is widely used for calculating channel thickness dependent band structure of any material, at a particular temperature, where TB parameters are defined. For elementary semiconductors like Si, Ge and compound semiconductors like GaAs, these TB parameters are generally defined at only 0 K and 300 K. This limits the ability of the TB approach to simulate the electrostatics of these devices at any other intermediate temperatures.</div><div>In this work, we analyze the variation of band structure for Si, Ge and GaAs over different channel thicknesses at 0 K and 300 K (for which TB parameters are available), and show that the band curvature at the band minima has minor variation with temperature, whereas the change of band gap significantly affects the channel electrostatics. Based on this finding, we propose an approach to simulate the electrostatics of UTB devices, at any temperature between 0 K and 300 K, using TB parameters defined at 0 K, along with a suitable channel thickness and temperature dependent band gap correction. </div>

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The reliability of the semi-empirical tight-binding method for band structure calculations

Journal of Physics C Solid State Physics ◽

10.1088/0022-3719/6/23/014 ◽

1973 ◽

Vol 6 (23) ◽

pp. 3403-3412 ◽

Cited By ~ 4

Author(s):

F Casula ◽

D R Edmondson

Keyword(s):

Band Structure ◽

Tight Binding ◽

Band Structure Calculations ◽

Tight Binding Method ◽

Semi Empirical ◽

Structure Calculations

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Temperature dependent Band gap Correction model using tight-binding approach for UTB device simulations

10.36227/techrxiv.18257963.v1 ◽

2022 ◽

Author(s):

Nalin Vilochan Mishra ◽

Ravi Solanki ◽

Harshit Kansal ◽

Aditya S Medury

Keyword(s):

Band Structure ◽

Band Gap ◽

Tight Binding ◽

Thin Body ◽

Temperature Dependent ◽

Minor Variation ◽

Correction Model ◽

Wide Range ◽

Channel Thickness ◽

Semi Empirical

<div>Ultra-thin body (UTB) devices are being used in many electronic applications operating over a wide range of temperatures. The electrostatics of these devices depends on the band structure of the channel material, which varies with temperature as well as channel thickness. The semi-empirical tight binding (TB) approach is widely used for calculating channel thickness dependent band structure of any material, at a particular temperature, where TB parameters are defined. For elementary semiconductors like Si, Ge and compound semiconductors like GaAs, these TB parameters are generally defined at only 0 K and 300 K. This limits the ability of the TB approach to simulate the electrostatics of these devices at any other intermediate temperatures.</div><div>In this work, we analyze the variation of band structure for Si, Ge and GaAs over different channel thicknesses at 0 K and 300 K (for which TB parameters are available), and show that the band curvature at the band minima has minor variation with temperature, whereas the change of band gap significantly affects the channel electrostatics. Based on this finding, we propose an approach to simulate the electrostatics of UTB devices, at any temperature between 0 K and 300 K, using TB parameters defined at 0 K, along with a suitable channel thickness and temperature dependent band gap correction. </div>

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A quantitative evaluation of computational methods to accelerate the study of alloxazine-derived electroactive compounds for energy storage

Scientific Reports ◽

10.1038/s41598-021-83605-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Qi Zhang ◽

Abhishek Khetan ◽

Süleyman Er

Keyword(s):

Energy Storage ◽

Density Functional ◽

Tight Binding ◽

Computational Cost ◽

Redox Potentials ◽

Storage Compounds ◽

Computational Screening ◽

Chemical Descriptor ◽

Lowest Unoccupied Molecular Orbital ◽

Semi Empirical

AbstractAlloxazines are a promising class of organic electroactive compounds for application in aqueous redox flow batteries (ARFBs), whose redox properties need to be tuned further for higher performance. High-throughput computational screening (HTCS) enables rational and time-efficient study of energy storage compounds. We compared the performance of computational chemistry methods, including the force field based molecular mechanics, semi-empirical quantum mechanics, density functional tight binding, and density functional theory, on the basis of their accuracy and computational cost in predicting the redox potentials of alloxazines. Various energy-based descriptors, including the redox reaction energies and the frontier orbital energies of the reactant and product molecules, were considered. We found that the lowest unoccupied molecular orbital (LUMO) energy of the reactant molecules is the best performing chemical descriptor for alloxazines, which is in contrast to other classes of energy storage compounds, such as quinones that we reported earlier. Notably, we present a flexible in silico approach to accelerate both the singly and the HTCS studies, therewithal considering the level of accuracy versus measured electrochemical data, which is readily applicable for the discovery of alloxazine-derived organic compounds for energy storage in ARFBs.

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Thermal Properties of Divalent Metal Oxides: CaO as a Prototype

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.209.190 ◽

2013 ◽

Vol 209 ◽

pp. 190-193

Author(s):

Nisarg K. Bhatt ◽

Brijmohan Y. Thakore ◽

P.R. Vyas ◽

A.Y. Vahora ◽

Asvin R. Jani

Keyword(s):

Density Functional ◽

Tight Binding ◽

Mean Field ◽

Field Potential ◽

Theoretical Data ◽

Test Case ◽

Generalized Gradient ◽

Core Electrons ◽

Vibrational Free Energy ◽

Semi Empirical

Commonly employed quasiharmonic approximation (QHA) is inadequate to account for intrinsic anharmonism such as phonon-phonon interaction, vacancy contribution, etc. Though anharmonic contributions are important at high temperatures and low pressure, complete ab initio calculations are scanty due largely to laborious computational requirements. Nevertheless, some simple semi-empirical schemes can be used effectively to incorporate the anharmonism. In this regards, in the present study we have proposed a simple computational scheme to include the effect of vacancy directly into the description within the mean-field potential approach, which calculates vibrational free energy of ions. Validity of the scheme is verified by taking calcium oxide as a test case. Equilibrium properties at (T,P) = (0,0) condition is obtained within the tight-binding second-moment approximation (TB-SMA), whose parameters were determined through first principles density functional theory. Kohn-Sham equations for core electrons were solved using ultrasoft plane-wave pseudopotential employing the generalized gradient approximation for exchange and correlation. Present findings for thermal expansion and high-T EOS clearly show perceptible improvement over the case when vacancy contribution was not included. Some related thermodynamic properties are also calculated and compared with the available experimental and theoretical data.

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