scholarly journals Evaluating Fast Methods for Static Polarizabilities on Extended Conjugated Oligomers

2021 ◽  
Author(s):  
Danielle Heiner ◽  
Dakota Folmsbee ◽  
Luke Langkamp ◽  
Geoffrey Hutchison
Keyword(s):  
Correction Factor ◽  
Dispersion Model ◽  
Tight Binding ◽  
Basis Set ◽  
Basis Sets ◽  
Calculation Methods ◽  
Benchmark Study ◽  
Tight Binding Method ◽  
Linear Correction ◽  
Semi Empirical

Given the importance of accurate polarizability calculations to many chemical applications, coupled with the need for efficiency when calculating the properties of sets of molecules or large oligomers, we present a benchmark study examining possible calculation methods for polarizable materials. We first investigate the accuracy of highly-efficient semi-empirical tight-binding method GFN2-xTB, and the popular D4 dispersion model, comparing its predicted additive polarizabilities to ωB97X-D results for a subset of PubChemQC and a compiled benchmark set of molecules spanning polarizabilities from approximately 3-600 Å^3, with a few compounds in the range of approximately 1200-1400 Å^3. Although we find GFN2 to have large errors with polarizability calculations, on large oligomers it would appear a quadratic correction factor can remedy this. We also compare the accuracy of DFT polarizability calculations run using basis sets of varying size and level of augmentation, determining that a non-augmented basis set may be used for highly polarizable species in conjunction with a linear correction factor to achieve accuracy extremely close to that of aug-cc-pVTZ.

scholarly journals Evaluating Fast Methods for Static Polarizabilities on Extended Conjugated Oligomers

2021 ◽  
Author(s):  
Danielle Heiner ◽  
Dakota Folmsbee ◽  
Luke Langkamp ◽  
Geoffrey Hutchison
Keyword(s):  
Correction Factor ◽  
Dispersion Model ◽  
Tight Binding ◽  
Basis Set ◽  
Basis Sets ◽  
Calculation Methods ◽  
Benchmark Study ◽  
Tight Binding Method ◽  
Linear Correction ◽  
Semi Empirical

Given the importance of accurate polarizability calculations to many chemical applications, coupled with the need for efficiency when calculating the properties of sets of molecules or large oligomers, we present a benchmark study examining possible calculation methods for polarizable materials. We first investigate the accuracy of highly-efficient semi-empirical tight-binding method GFN2-xTB, and the popular D4 dispersion model, comparing its predicted additive polarizabilities to ωB97X-D results for a subset of PubChemQC and a compiled benchmark set of molecules spanning polarizabilities from approximately 3-600 Å^3, with a few compounds in the range of approximately 1200-1400 Å^3. Although we find GFN2 to have large errors with polarizability calculations, on large oligomers it would appear a quadratic correction factor can remedy this. We also compare the accuracy of DFT polarizability calculations run using basis sets of varying size and level of augmentation, determining that a non-augmented basis set may be used for highly polarizable species in conjunction with a linear correction factor to achieve accuracy extremely close to that of aug-cc-pVTZ.

Determination of the high c/a ratio of hexagonal metals with a semi-empirical tight-binding method

2000 ◽  
Vol 17 (2-4) ◽  
pp. 249-254 ◽  
Author(s):  
A Béré ◽  
J Chen ◽  
A Hairie ◽  
G Nouet ◽  
E Paumier
Keyword(s):  
Tight Binding ◽  
Tight Binding Method ◽  
Semi Empirical ◽  
Hexagonal Metals

Basal stacking faults and (10&1macr;2) twin energies by a semi-empirical tight-binding method for zinc and cadmium

2004 ◽  
Vol 241 (11) ◽  
pp. 2482-2488 ◽  
Author(s):  
A. Béré ◽  
J. Chen ◽  
A. Hairie ◽  
G. Nouet ◽  
E. Paumier
Keyword(s):  
Tight Binding ◽  
Stacking Faults ◽  
Tight Binding Method ◽  
Semi Empirical

An Improved TB Method for the AlGaN/GaN Superlattice

2012 ◽  
Vol 549 ◽  
pp. 41-44
Author(s):  
Jun Feng Chen ◽  
Xiang Zhen Yu
Keyword(s):  
Calculation Result ◽  
Polarization Effect ◽  
Dispersion Model ◽  
Tight Binding ◽  
Nonlinear Transport ◽  
Potential Wells ◽  
Al Content ◽  
Strong Polarization ◽  
Tight Binding Method ◽  
Improved Model

The tradition energy dispersion model can not match the experiment results of the AlGaN/GaN superlattice with strong polarization effect. Thus we propose a new dispersion model from the improved tight binding method. In this model, the couple of wavefunctions from more potential wells are considered. To a AlGaN/GaN superlattice with 1.5nm well length, 1nm barrier length and 25% Al content, the calculation result shows that the improved model are much more precise than the tradition model. This improved dispersion model can be used in the study of the nonlinear transport of AlGaN/GaN superlattice.

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.

scholarly journals Random Versus Systematic Errors in Reaction Enthalpies Computed Using Semi-empirical and Minimal Basis Set Methods

2018 ◽  
Author(s):  
Jimmy Kromann ◽  
Alexander Welford ◽  
Anders Steen Christensen ◽  
Jan H. Jensen
Keyword(s):  
Tight Binding ◽  
Original Study ◽  
Basis Set ◽  
Semiempirical Methods ◽  
Random Errors ◽  
Minimal Basis ◽  
Dft Methods ◽  
Heavy Atoms ◽  
Increase In Accuracy ◽  
Semi Empirical

The connectivity-based hierarchy (CBH) protocol for computing accurate reaction enthalpies developed by Sengupta and Raghavachari is tested for fast <i>ab initio</i> methods (PBEh-3c, HF-3c, and HF/STO- 3G), tight-binding DFT methods (GFN-xTB, DFTB, and DFTB-D3), and NDDO-based semiempirical methods (AM1, PM3, PM6, PM6-DH+, PM6-D2, PM6-D3H+, PM6-D3H4X, PM7, and OM2) using the same set of 25 reactions as in the original study. For the CBH-2 scheme, which reflects the change in the immediate chemical environment of all the heavy atoms, the respective MUE relative to G4 for PBEh-3c, HF-3c, HF/STO-3G, GFN-xTB, DFTB-D3, DFTB, PM3, AM1, PM6, PM6-DH+, PM6-D3, PM6-D3H+, PM6-D3H4X, PM7, and OM2 are 1.9, 2.4, 3.0, 3.9, 3.7, 4.5, 4.8, 5.5, 5.4, 5.3, 5,4, 6.5, 5.3, 5.2, and 5.9 kcal/mol, with a single outlier removed for HF-3c, PM6, PM6-DH+, PM6-D3, PM6-D3H4X, and PM7. The increase in accuracy for the NDDO-based methods is relatively modest due to the random errors in predicted heats for formation.

scholarly journals On the hydrogen activation by frustrated Lewis pairs in the solid state: benchmark studies and theoretical insights

2017 ◽  
Vol 375 (2101) ◽  
pp. 20170006 ◽  
Author(s):  
Lei Liu ◽  
Jan Gerit Brandenburg ◽  
Stefan Grimme
Keyword(s):  
Solid State ◽  
Tight Binding ◽  
Experimental Studies ◽  
Basis Set ◽  
Small Molecule Activation ◽  
Computationally Efficient ◽  
Generalized Gradient ◽  
Frustrated Lewis Pairs ◽  
Semi Empirical ◽  
Lewis Pairs

Recently, the concept of small molecule activation by frustrated Lewis pairs (FLPs) has been expanded to the solid state showing a variety of interesting reactivities. Therefore, there is a need to establish a computational protocol to investigate such systems theoretically. In the present study, we selected several FLPs and applied multiple levels of theory, ranging from a semi-empirical tight-binding Hamiltonian to dispersion corrected hybrid density functionals. Their performance is benchmarked for the computation of crystal geometries, thermostatistical contributions, and reaction energies. We show that the computationally efficient HF-3c method gives accurate crystal structures and is numerically stable and sufficiently fast for routine applications. This method also gives reliable values for the thermostatistical contributions to Gibbs free energies. The meta-generalized gradient approximated TPSS-D3 evaluated in a projector augmented plane wave basis set is able to produce sufficiently accurate reaction electronic energies. The established protocol is intended to support experimental studies and to predict new reactions in the emerging field of solid-state FLPs. This article is part of the themed issue ‘Frustrated Lewis pair chemistry’.

Optical Signature of the GaN (1010) Surface

1996 ◽  
Vol 449 ◽  
Author(s):  
C. Noguez ◽  
R. Esquivel-Sirvent ◽  
D. R. Alfonso ◽  
S. E. Ulloa ◽  
D. A. Drabold
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Dielectric Response ◽  
Theoretical Study ◽  
Tight Binding ◽  
Electronic Transitions ◽  
Surface Electronic Structure ◽  
Optical Signature ◽  
Tight Binding Method ◽  
Semi Empirical

ABSTRACTWe present a theoretical study of the optical properties of the GaN (1010) surface. We employed a semi-empirical tight-binding method to calculate the surface electronic structure. The parameters were adjusted to reproduce the correct band structure of the bulk wurzite GaN. These parameters were interpolated to the surface using Harrison’s rule. From the surface electronic structure the surface dielectric response was obtained. The dielectric response is analized in terms of surface-surface, and surface-bulk electronic transitions.

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