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Vahdat Rafee

Publications and source records attributed to Vahdat Rafee.

3 recordsLinked to original sources

Local field correction effects on quasi-particle inelastic scattering rate in a coupled-quantum-layers system at finite temperature

Local field correction effects on intra-layer inelastic scattering rate of interacting electrons are theoretically investigated in a coupled-quantum-wells structure, at finite temperature. At first, temperature dependent dynamic dielectric function is calculated using random phase approximation (RPA). Then, local field correction effects are considered in calculations by employing short-range effects of exchange-correlation holes around electrons. We employ Hubbard, finite-temperature Hubbard and STLS approximations. Finally, quasi-particle inelastic scattering rate is calculated using the imaginary part of the electron self-energy within GW method. The results show that quasi-particle inelastic scattering rate is reduced, when a local field correction is employed, at any temperature, wave vector and electron density.

cond-mat.mes-hall

A Theoretical Study on Crystallization of Polyethylene Using Modified Weighted Density Approximation (MWDA)

In this article, the crystallization of Polyethylene is investigated by the modified weighted density approximation. Also a direct correlation function of Polyethylene based on the RISM theory is used. The free energy of a Polyethylene is calculated using density functional theory. The crystallization together with solid and liquid densities are calculated and finally compared with the PRISM simulations and experimental results. The result obtained by modified weighted density approximation MWDA is shown to be in a better agreement with the experimental results rather than the PRISM simulations.

cond-mat.soft

Effects of Sol concentration on the structural and optical properties of SnO2 Nanoparticle

In this paper, the effects of changes in Sol concentration on the structural and optical properties of SnO2 Nanoparticles are studied through the Sol-Gel method. SnO2 Nanoparticles are produced from different SnO2 solution concentrations (0.1, 0.3 and 0.5 mol/L) at room temperature. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis is used to investigate the effects of changes in Sol concentration on the crystalline and surface morphology of Nanoparticles. The XRD pattern shows that the particles are in the standard tetragonal phase of SnO2. The crystallites size are 11.7nm, 18.8nm, and 74.8nm, for 0.1 M, 0.3M and 0.5 M of concentration respectively. The average size of SnO2 particles decreases by a reduction in the Sol concentration. The band gap value is 4.07ev, 4.28ev and 4.36ev for 0.1M, 0.3M and 0.5M of concentration respectively. The UV-visible analysis shows that decreasing the Sol concentration will cause the absorption edge shift to the shorter wavelengths, because decreasing the Sol concentration will reduce the Nanoparticles size, and smaller Nanoparticles size absorb shorter wavelengths better and also increase the band gap.

cond-mat.mes-hall