Transfer Integrals and Band Structures in (Et)2X Salts

1989 ◽  
Vol 173 ◽  
Author(s):  
Oliver H. Leblanc ◽  
Margaret L. Blohm ◽  
Richard P. Messmer
Keyword(s):  
Low Temperature ◽  
Nearest Neighbor ◽  
Spherical Wave ◽  
Tight Binding ◽  
Ab Initio Method ◽  
Energy Bands ◽  
Hubbard Hamiltonian ◽  
Transfer Integrals ◽  
Semi Empirical ◽  
Very Low Temperature

ABSTRACTTransfer integrals (tij) between pairs of nearest neighbor ET molecules were calculated by an ab initio method. Tight-binding one-electron energy bands constructed from the tij are similar to those previously calculated by Mori and by Whangbo and their coworkers by semi-empirical, extended Hückel methods, but quite different from those found by Kübler et al. in β-(ET)2I3 using the augmented spherical wave (ASW) method. However, all these band models are suspect. The Hubbard on-site repulsion parameter U is estimated to be about twice the band widths, indicating that a full treatment of the Hubbard hamiltonian is needed. Also, polaron effects appear to control transport except at very low temperature.

scholarly journals Electronic properties of bilayer sheets forming moiré patterns

2021 ◽  
Vol 24 (1) ◽  
pp. 13701
Author(s):  
W.S. Wu-Mei ◽  
R.R. Rey-González
Keyword(s):  
Boron Nitride ◽  
Nearest Neighbor ◽  
Periodic Structures ◽  
Tight Binding ◽  
Electronic Band ◽  
Moire Patterns ◽  
Energy Approximation ◽  
Electronic Dispersion ◽  
Semi Empirical ◽  
Moiré Patterns

In this article, we report the electronic band structures of hexagonal bilayer systems, specifically, rotated graphene-graphene and boron nitride-boron nitride bilayers, by introducing an angle between the layers and forming new periodic structures, known as moiré patterns. Using a semi-empirical tight-binding approach with a parametrized hopping parameter between the layers, using one orbital per-site approximation, and taking into account nearest-neighbor interactions only, we found he electronic dispersion relations to be around K points in a low energy approximation. Our results show that graphene bilayers exhibit zero band gap for all angles tested in this work. In boron nitride bilayers, the results reveal a tunable bandgap that satisfies the prediction of the bandgap found in one-dimensional diatomic systems presented in the literature.

Semi-Empirical Tight Binding Calculations for the Energy Bands of the Diamond and Zincblende Type Semiconductors

1984 ◽  
Vol 122 (2) ◽  
pp. 661-667 ◽  
Author(s):  
S. N. Sahu ◽  
J. T. Borenstein ◽  
V. A. Singh ◽  
J. W. Corbett
Keyword(s):  
Tight Binding ◽  
Energy Bands ◽  
Semi Empirical

RESISTIVITY OF TmSe UNDER PRESSURE AT VERY LOW TEMPERATURE

1980 ◽  
Vol 41 (C5) ◽  
pp. C5-177-C5-180
Author(s):  
J. Flouquet ◽  
P. Haen ◽  
F. Holtzberg ◽  
F. Lapierre ◽  
J. M. Mignot ◽  
...  
Keyword(s):  
Low Temperature ◽  
Very Low Temperature

Can fluorosyl hydride be formed or even prepared?

1990 ◽  
Vol 55 (4) ◽  
pp. 890-895
Author(s):  
Rudolf Zahradník ◽  
B. Andes Hess
Keyword(s):  
Low Temperature ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Solid Matrix ◽  
Vibrational Characteristics ◽  
Very Low Temperature

HFO and HClO (fluorosyl and chlorosyl hydrides) and isomeric molecules HOF and HOCl (hypofluorous and hypochlorous acids) have been studied theoretically. On the basis of nonempiracal quantum chemical calculations (MP2, MP4 and CCD/6-311G**) geometry, energy and vibrational characteristics are analyzed and it is concluded that there is a poor chance to observe formation of HFO. Possibly, bombardment of HF in a solid matrix by 16O could lead at very low temperature to HFO.

scholarly journals Silver‐Promoted High‐Performance (Ag,Cu)(In,Ga)Se 2 Thin‐Film Solar Cells Grown at Very Low Temperature

Solar RRL ◽  
2021 ◽  
pp. 2100108
Author(s):  
Shih-Chi Yang ◽  
Jordi Sastre ◽  
Maximilian Krause ◽  
Xiaoxiao Sun ◽  
Ramis Hertwig ◽  
...  
Keyword(s):  
Thin Film ◽  
Solar Cells ◽  
Low Temperature ◽  
High Performance ◽  
Thin Film Solar Cells ◽  
Very Low Temperature

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

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.

Thermal Properties of Divalent Metal Oxides: CaO as a Prototype

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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