جستجوی مقالات مرتبط با کلیدواژه « چگالی حالات جزئی » در نشریات گروه « فیزیک »

The electronic properties of MAPbX3(MA= CH3NH3+) units employing the experimental cell parameters (6.33,5.95 and5.66 Å for X = I,Br and Cl, respectively),FAPbX3(FA=( CH-(NH2)2+) units employing the experimental cell parameters (6.36 , 5.99 and5.60 Å for X = I ,Br and Cl, respectively) perovskite in the cubic phase are systematically studied using the first-principles calculations. We correlate our experimental results with first-principles theory and provide an insight into important parameters like; lattice constants, electronic structure , static and high-frequency dielectric constants, Reflection coefficient, Absorption coefficient , Optical conductivity , Refractive index,in these perovskite .Our calculations are performed using the Quantum-Espresso pakage in the framework of density functional theory (DFT). The projector augmented-wave (PAW) pseudopotentials are used within energy cutoff of 408 Ev for the plane-wave basis functions.For the exchange-correlationfunctional, the generalized gradient approximation(GGA) of Perdew-Burke-Ernzerhof(PBE) is used to relax the structural parameters. We substituted I- to Br- to Cl- in order to tune the bandgap from 1.6 eV to 2.4 ev to 3.2 eV of these materials. Electronic structure calculations reveal that electronic properties are mainly governed by Pb 6p and halide p orbitals. spin-orbit coupling (SOC) is included in all the calculations. All calculations reported in agreement with experimental data.

DFT ab-initio calculation (using plane waves and pseudo-potential approach) has been employed for a systematic study of potassium substitution in YBa2-xKxCu3O7 samples. The electronic structure، energy levels and the density of states (DOS) with different potassium doping amounts (x=0. 16، 0. 25، 0. 5، 0. 75) were calculated under the generalized gradient approximation (GGA). The substitution of potassium changes the electronic band structure and DOS. These modifications are responsible for empirical reports of decreasing the TC with increasing of the potassium. In addition، our results about the variation of lattice parameters (a، b and c) of the system are in good agreement with experimental reports according to the Rietveld refinement of XRD data.