scholarly journals A theoretical study on photo absorption in silicon decorated boron clusters (BnSi, n=7-10)

2021 ◽  
Vol 2070 (1) ◽  
pp. 012051
Author(s):  
Ankita Jaiswal ◽  
Shakti S Ray ◽  
Sridhar Sahu
Keyword(s):  
Optical Absorption ◽  
Oscillator Strength ◽  
Absorption Spectra ◽  
Density Functional ◽  
Visible Region ◽  
Basis Set ◽  
Functional Study ◽  
Strength Analysis ◽  
Optical Absorption Spectra ◽  
Boron Clusters

Abstract In this work, we have studied the optical absorption spectra of small boron clusters doped with single silicon atom (BnSi, n=7-10) and is reported employing CAM-B3LYP functional with 6-311+G(d) basis –set within the framework of time dependent density functional study (TD-DFT). We have computed excitation energy, oscillator strength, wavelength and the corresponding orbital transitions associated with a given oscillator strength. Analysis of optical absorption spectra of studied clusters shows that most of the absorption peaks are found in the ultraviolet-visible (UV-Vis) region (200 nm-700 nm). The major peaks are found to fall in UV region along with some weaker peaks at visible region. The most intense peak is recorded for B8Si cluster at 232 nm and oscillator strength of 0.084. This peak is associated with the orbital transition from H-4→L+1.

Electronic excitations of stable fullerene-like GaP clusters

2004 ◽  
Vol 854 ◽  
Author(s):  
Giuliano Malloci ◽  
Giancarlo Cappellini ◽  
Giacomo Mulas ◽  
Guido Satta
Keyword(s):  
Optical Absorption ◽  
Absorption Spectra ◽  
Density Functional ◽  
Electronic Excitations ◽  
Optical Absorption Spectra ◽  
Functional Theory ◽  
Quasi Particle ◽  
New Class ◽  
Excitonic Effects ◽  
Homo Lumo

ABSTRACTWe present quasi-particle (QP) corrections to the electronic energies for small GaP fullerenes, a new class of nanoscaled materials predicted to be stable and to show spontaneous formation. Using Time-Dependent Density Functional Theory we also computed the optical absorption spectra. The comparison between single-particle and optical absorption spectra yields strong excitonic effects with bonding energy up to 3.5 eV. The QP corrected HOMO-LUMO energy gaps confirm the high stability predicted for such molecules using ground-state computational schemes. The present results can be useful to identify the successful synthesis of these systems via optical absorption and QP spectra.

scholarly journals Electronic characteristics of CdS quantum dots with defects

2020 ◽  
pp. 28
Author(s):  
I. M. Kupchak ◽  
D. V. Korbutyak ◽  
N. F. Serpak
Keyword(s):  
Quantum Dots ◽  
Optical Absorption ◽  
Valence Band ◽  
Absorption Spectra ◽  
Density Functional ◽  
Optical Absorption Spectra ◽  
Cds Quantum Dots ◽  
Generalized Gradient ◽  
Substitutional Impurity ◽  
Cadmium Vacancy

Using the density functional theory and the generalized gradient approximation, we calculated the atomic structure, the density of electronic states, and the optical absorption spectra of CdS quantum dots containing intrinsic defects — a cadmium vacancy VCd and an interstitial sulfur atom SI, and substitutional impurities — zinc and copper in place of the atom cadmium — ZnCd and CuCd, respectively. The calculations were performed for the Cd33S33 cluster corresponding to the so-called “magic” size of the quantum dot. This size has a minimum of dangling bonds at the surface and allows the using of such a cluster without the passivation. The structural relaxation during the formation of such defects and the distribution of the wave function of the state corresponding to the top of the valence band are analyzed in details. It has been shown that the cadmium vacancy forms local states in the band gap of CdS nanocrystals, and can serve as centers of radiative recombination. Other defects form energy levels in the depths of the valence band or near its top, but whose energy positions do not correspond to the band maxima in the experimental photoluminescence spectra of CdS quantum dots, both undoped and doped with zinc. The calculated optical absorption spectra demonstrate a strong peak in the region of fundamental absorption of CdS for a cluster containing a substitutional impurity of CuCd, in contrast to other systems where no such peaks are observed. In addition, the replacement of the cadmium atom with copper leads to a decrease in the number of chemical bonds to three and, accordingly, to the largest relaxation among the systems studied. This feature is caused by the crystal structure inhomogeneity of copper sulfide CuxS, which, depending on stoichiometry, can be either a semiconductor or a metal.

scholarly journals Ring fusion in tetrathienylethene cored perylene diimide tetramers affords acceptors with strong and broad absorption in the near-UV to visible region

2020 ◽  
Vol 8 (48) ◽  
pp. 17237-17244
Author(s):  
Qiao He ◽  
Flurin D. Eisner ◽  
Drew Pearce ◽  
Thomas Hodsden ◽  
Elham Rezasoltani ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Dft Calculations ◽  
Absorption Spectra ◽  
Organic Photovoltaics ◽  
Visible Region ◽  
Perylene Diimide ◽  
Optical Absorption Spectra ◽  
Broad Absorption ◽  
Ring Fusion

Two PDI tetramers with a central tetrathienylethene core were investigated as non-fullerene acceptors in organic photovoltaics and the dramatic differences in their optical absorption spectra were rationalised on the basis of DFT calculations.

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