scholarly journals A Theoretical Study of Bulk Tungsten (W) Based on Momentum Transfer (q-Dependent)

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
D. P. Rai ◽  
R. K. Thapa

The ground state electronic properties of bulk (W) were studied within the density functional theory (DFT). We have also analyzed the momentum- (q-) dependent loss function, dielectric constant, and optical conductivity (OC) within TD-DFT random-phase approximation (RPA). The loss function is plotted in the energy range 0–55 eV. The energy loss function spectrum shows four prominent peaks, two lower peaks below along with two sharp peaks above 30 eV. The different nature of peaks depends on the momentum transfer q. The peak caused by interband transition showed a less pronounced dispersion. From the dielectric function curve we have predicted the plasmon excitation at around 1.75 eV and calculated the corresponding plasma frequency (ωp)=26.585×1014 s−1.

Molecules ◽  
2019 ◽  
Vol 24 (17) ◽  
pp. 3134 ◽  
Author(s):  
Zhi-Dan Sun ◽  
Jiang-Shan Zhao ◽  
Xue-Hai Ju ◽  
Qi-Ying Xia

On the basis of thieno(3,2-b)thiophene and dithieno[3,2-b:2′,3′-d]thiophene (T2 and T3 moieties) as π-linker, the A, D and S series dyes were designed to investigate the effect of the introducing N+ as an “electron trap” into T2 and T3 on the properties of the dyes. The optimized structures, electronic and optical properties were investigated by the density functional theory (DFT) and time-dependent DFT (TD-DFT). The results show that the properties of the dyes are sensitive to the N+ position in π-linkers. D series dyes with electron-withdrawing units located near the donor have better properties than the corresponding A series with the electron-withdrawing units located near the acceptor. For A and D series, the N+ modified dye named T2N+1-d displays the largest red shift of the UV–vis absorption, the maximum integral values of the adsorption-wavelength curves over the visible light, the highest light harvesting efficiency (LHE, 0.996), and the strongest adsorption energy (−44.33 kcal/mol). T2N+1-d also has a large driving force of hole injection (ΔGinj, −0.74 eV), which results in a more efficient hole injection. Bearing a lengthier π-linker than T2N+1-d, the properties of T2N+1-s are further improved. T2N+1-d moiety or its increased conjugated derivatives may be a promising π-linker.


2014 ◽  
Vol 989-994 ◽  
pp. 220-223
Author(s):  
Chao Xu ◽  
Dong Chen

Using quantum mechanics plane-wave approach based on the density functional theory, the lattice constants of NixAl at different Ni concentrations (x=1, 3) are predicted. Optical properties such as dielectric function, energy loss function and reflectivity are also investigated. Results show that with the increase of Ni constituent, the location of the peak in loss function moves to the lower energy region, but the peak height increases. At 0eV, the reflectivity increases rapidly with the Ni concentration. The reflectivity of NiAl and Ni3Al are pronounced in the UV region (not in the visible light region). The dielectric properties, namely the real and imaginary parts of the dielectric function, changed significantly with Ni constituent.


1992 ◽  
Vol 10 (2) ◽  
pp. 299-309 ◽  
Author(s):  
T. Błeński ◽  
B. Cichocki

We propose a new formalism to electronic polarizability of dense, partially ionized plasmas. This formalism is based upon the density functional theory for the electronic equilibrium, the random phase approximation for the density response of electrons, and the cluster expansion in the averaging over ionic configurations. The first term in the final cluster expansion for the imaginary part of electron polarizability corresponds to the Lindhard dielectric function formula. The second term contains the electronic states of the average atom. The additional effects that result from this theory are: channel mixing (screening), “inverse Bremstrahlung” corrections, and free-bound electronic transitions. Our approach allows the plasma (collective) and atomic physics phenomena to be treated in the frame of one formalism. The theory can be applied for stopping power and opacity calculations.


2019 ◽  
Vol 48 (47) ◽  
pp. 17605-17611
Author(s):  
Paola Nava ◽  
Momar Toure ◽  
Amel Abdou Mohamed ◽  
Jean-Luc Parrain ◽  
Olivier Chuzel

The mechanism of the intramolecular enantioselective rhodium(i)-catalyzed hydroboration of NHC-boranes is investigated by experiments and calculations, using Density Functional Theory and Random Phase Approximation methods.


2020 ◽  
Vol 8 (1) ◽  
pp. 219-227 ◽  
Author(s):  
Yu Gao ◽  
Wei Guan ◽  
Li-Kai Yan ◽  
Zhong-Min Su

Theoretical calculations based on the density functional theory (DFT) and time-dependent DFT (TD-DFT) were employed to screen efficient acceptor group candidates for POM-based dyes.


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