Accurate determination of band gaps within density functional formalism

2013 ◽  
Vol 87 (23) ◽  
Author(s):  
Prashant Singh ◽  
Manoj K. Harbola ◽  
Biplab Sanyal ◽  
Abhijit Mookerjee
Keyword(s):  
Density Functional ◽  
Accurate Determination ◽  
Band Gaps ◽  
Functional Formalism

Weak intra- and intermolecular interactions in a binaphthol imine: an experimental charge-density study on (±)-8′-benzhydrylideneamino-1,1′-binaphthyl-2-ol

2009 ◽  
Vol 65 (6) ◽  
pp. 757-769 ◽  
Author(s):  
Louis J. Farrugia ◽  
Pavel Kočovský ◽  
Hans Martin Senn ◽  
Štěpán Vyskočil
Keyword(s):  
Charge Density ◽  
Intermolecular Interactions ◽  
Density Functional ◽  
Topological Analysis ◽  
Accurate Determination ◽  
Phenyl Group ◽  
X Ray Diffraction ◽  
Pairwise Interactions ◽  
Weak Intermolecular Interactions

The charge density in (±)-8′-benzhydrylideneamino-1,1′-binaphthyl-2-ol (1) has been studied experimentally using Mo Kα X-ray diffraction at 100 K, and by theory using density-functional thoery (DFT) calculations at the B3LYP/6-311++G** level. The nature of the weak intramolecular peri-C...N, CH...π, H...H and C(π)...C(π) interactions has been examined by topological analysis using the Quantum Theory of Atoms in Molecules (QTAIM) approach. An analysis of the density ρ(r), the Laplacian of the density ∇2ρ(r b) and other topological properties at the bond-critical points were used to classify these interactions. The study confirms the presence of the intramolecular CH...π interaction in (1), which was previously suspected on geometrical grounds. An analysis of the ellipticity profiles along the bond paths unambiguously shows the π-delocalization between the imine unit and one N-phenyl group. The weak intermolecular interactions in the crystal of (1) were examined experimentally and theoretically through the pairwise interactions of the seven independent dimeric pairs of (1) responsible for the set of unique intermolecular interactions, and also through examination of the Hirshfeld surface d norm property. The theoretical dimeric-pair calculations used the BLYP-D functional which supplements the exchange-correlational functional with an empirical dispersion term to provide a more accurate determination of the energies for the weak intermolecular interactions.

scholarly journals Determination of the Effect of Chalcogen Replacement on the Interaction Site and Transition State of the Substituted Analogues of Formaldehyde with Aldehyde Oxidase: A Density Functional Theory Approach

2019 ◽  
pp. 25-42
Author(s):  
Tadege Belay
Keyword(s):  
Density Functional Theory ◽  
Transition State ◽  
Active Site ◽  
Density Functional ◽  
Aldehyde Oxidase ◽  
Theory Approach ◽  
Functional Formalism ◽  
Functional Theory ◽  
Reported Data

Aldehyde oxidase (AO) enzyme is known to oxidize aldehydes. One of the aldehydes, formaldehyde, is known to inhibit xanthine oxidase as it turns over. However, there is no reported data whether it behaves the same when it reacts with aldehyde oxidase. Similarly, the effect of chalcogen replacement on nucleophilic reaction and charge density distribution on the substituted analogs of formaldehyde and their behavior during catalysis has never been studied. Therefore, the research is intended to probe the most tractable substrate that interacts to the reductive half-reaction active site of AO. Therefore, a density functional theory of the B3LYP correlation functional formalism (DFT-B3LYP) methods was used to generate several parameters from the electronic structure calculations. Accordingly, the higher percentage (%) contribution to HOMO and energy barrier (kcal/mol) (0.099, -7.185040E+04) makes formaldehyde as the favored substrate for aldehyde oxidase, compared to thioformaldehyde (-0.245, -2.745113E+05) and selenoformaldehyde (-0.175, -1.529992E+06), respectively. In addition, the transition state structures for the active site bound to formaldehyde (ACT-FA), thioformaldehyde (ACT-THIO FA), and selenoformaldehyde (ACT-SELENO FA), respectively, were confirmed by one imaginary negative frequency (S-1) (-328.44, -430.266, and -624.854).

scholarly journals Density Functional Theory and Experimental Determination of Band Gaps and Lattice Parameters in Kesterite Cu2ZnSn(SxSe1–x)4

2020 ◽  
Vol 11 (24) ◽  
pp. 10463-10468
Author(s):  
Chuan-Jia Tong ◽  
Holly J. Edwards ◽  
Theodore D. C. Hobson ◽  
Ken Durose ◽  
Vinod R. Dhanak ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Experimental Determination ◽  
Density Functional ◽  
Lattice Parameters ◽  
Band Gaps ◽  
Functional Theory

Determination of symmetry reduced structures by a soft-phonon analysis in Ni2MnGa

2007 ◽  
Vol 1050 ◽  
Author(s):  
Tilmann Hickel ◽  
Matthe A. Uijttewaal ◽  
Blazej Grabowski ◽  
Jörg Neugebauer
Keyword(s):  
Phase Transition ◽  
Density Functional ◽  
Energy Surface ◽  
Accurate Determination ◽  
Martensitic Phase ◽  
Functional Theory ◽  
Lattice Constants ◽  
Martensitic Phase Transition ◽  
Phonon Spectra

AbstractThe shape memory effect of Ni2MnGa is closely related to the fact that the material undergoes a martensitic phase transition, which results in symmetry reductions and deformations when cooling down. However, there are still substantial uncertainties about the phase diagram in the martensitic phase. Particularly challenging is the determination of those phases, which are characterized by shuffling structures. We have applied density functional theory to this problem, which allows an accurate determination of the potential energy surface as a function of the lattice constants. Based on these results we compute ab initio phonon spectra and discuss in detail how they can be used to extract detailed information about the type of shuffling structures and to systematically and efficiently identify stable atomic configurations.

Electronic Stopping Power for Low Energy Ions

1985 ◽  
Vol 45 ◽  
Author(s):  
N. Azziz ◽  
K. W. Brannon ◽  
G. R. Srinivasan
Keyword(s):  
Effective Charge ◽  
Density Functional ◽  
Considerable Effect ◽  
Low Energy ◽  
Stopping Power ◽  
Target Electron ◽  
Functional Formalism ◽  
Low Energy Ions ◽  
Electronic Stopping Power

ABSTRACTA procedure to be used in ion implantation calculations has been developed to determine the stopping power of an ion at low energy as a function of its effective charge. The ion effective charge accounts for screening of the ion and has been found to have considerable effect on the stopping power through its dependence on the target electron density. Steps in the procedure include: the calculation of the Fermi momentum of the target, calculation of the relative velocity between the projectile and target electron cloud, determination of the screening distance for the ion, and calculation of the proton stopping power Sp according to the density-functional formalism. The ion stopping power is then is the ion effective charge. The procedure can be applied to semiconductors and metals. Comparisons are reported with the predictions of the Firsov and Lindhard methods which do not include any effective charge or shell structure considerations. The computer program MARLOWE has been modified to include this method for calculating the stopping power. Results in the form of implanted boron profiles in silicon will be presented.

A quantitative approach to inner shell losses

1978 ◽  
Vol 36 (1) ◽  
pp. 526-527 ◽  
Author(s):  
R.D. Leapman ◽  
P. Rez ◽  
D.F. Mayers
Keyword(s):  
Energy Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Accurate Determination ◽  
Background Intensity ◽  
Core Excitation ◽  
Quantitative Basis ◽  
Cross Section Differential ◽  
Bound Electrons

Microanalysis by EELS has been developing rapidly and though the general form of the spectrum is now understood there is a need to put the technique on a more quantitative basis (1,2). Certain aspects important for microanalysis include: (i) accurate determination of the partial cross sections, σx(α,ΔE) for core excitation when scattering lies inside collection angle a and energy range ΔE above the edge, (ii) behavior of the background intensity due to excitation of less strongly bound electrons, necessary for extrapolation beneath the signal of interest, (iii) departures from the simple hydrogenic K-edge seen in L and M losses, effecting σx and complicating microanalysis. Such problems might be approached empirically but here we describe how computation can elucidate the spectrum shape.The inelastic cross section differential with respect to energy transfer E and momentum transfer q for electrons of energy E0 and velocity v can be written as

Fast calibration of CBED patterns for quantitative analysis

1993 ◽  
Vol 51 ◽  
pp. 674-675
Author(s):  
M.A. Gribelyuk ◽  
M. Rühle
Keyword(s):  
Reciprocal Lattice ◽  
Accurate Determination ◽  
Incident Beam ◽  
Crystal Thickness ◽  
Structure Model ◽  
Beam Direction ◽  
Transmitted Beam ◽  
Reciprocal Vector ◽  
On Line

A new method is suggested for the accurate determination of the incident beam direction K, crystal thickness t and the coordinates of the basic reciprocal lattice vectors V1 and V2 (Fig. 1) of the ZOLZ plans in pixels of the digitized 2-D CBED pattern. For a given structure model and some estimated values Vest and Kest of some point O in the CBED pattern a set of line scans AkBk is chosen so that all the scans are located within CBED disks.The points on line scans AkBk are conjugate to those on A0B0 since they are shifted by the reciprocal vector gk with respect to each other. As many conjugate scans are considered as CBED disks fall into the energy filtered region of the experimental pattern. Electron intensities of the transmitted beam I0 and diffracted beams Igk for all points on conjugate scans are found as a function of crystal thickness t on the basis of the full dynamical calculation.

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