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We present first principles calculations of the electronic, structural and optical properties of the cubic perovskite CsSrF3 by using the full potential linearized augmented plane wave (FP-LAPW) plus local orbitals method with generalized gradient approximation (GGA) in the frame work of density functional theory. The calculated lattice constant is in a good agreement with the experimental result. The electronic band structure shows that the fundamental band gap is wide and direct at G point. The contribution of the different bands was analyzed from the total and partial density of states curves. The charge density plots show strong ionic bonding in Cs-F, ionic and weak covalent bonding between Sr and F. The calculated optical spectra viz., the dielectric function, optical refiectivity, absorption coefficient, real part of optical conductivity, refractive index, extinction coefficient and electron energy loss, are presented for the energy range of 0-30 eV.
W pracy opisano rezultaty badań teoretycznych struktury elektronowej - wykonanych w oparciu o wyniki obliczeń ab initio, przeprowadzonych za pomocą programu WIEN2k (metoda DFT FP-LAPW stowarzyszonych fal płaskich w pełnym potencjale krystalicznym w ramach formalizmu teorii funkcjonału gęstości) - oraz topologii gęstości elektronowej (w oparciu o formalizm QTAiM kwantowej teorii atomów w cząsteczkach R.F.W. Badera) dla wybranych modelowych roztworów stałych Ag(SbxSn1-x)Se2. Otrzymane wyniki poddane zostały szczegółowej analizie w kontekście wpływu obniżenia lokalnej symetrii i stopnia domieszkowania cyną na kształt i własności struktury elektronowej i topologicznych własności gęstości elektronowej w punktach krytycznych wiązań.
The results of theoretical studies of electronic structure, obtained by means of the full-potential linearized augmented plane wave method within DFT formalism as implemented in Wien2k package, and electron density topology and bonding, obtained by means of the Bader’s quantum theory of atoms in molecules topological analysis of total electron density derived from FP-LAPW calculations, were carried out f orchosen solid solutions of Ag(SbxSn1-x)Se2 and described in the paper. Detailed analysis of the obtained results from the point of view of the dependence of electronic structure and topological properties of bond critical points on local ordering and level of tin doping is presented.
In this paper the results of studies on the effect of pressure on hyperfine magnetic field (Bf) and isomer shift (IS) for Fe-bcc are presented. Two calculation methods were used: TB-LMTO (Tight Binding Linear Muffin-Tin) and FP-LAPW (Full Potential Linearized Augmented Plane Wave) and the obtained results have been compared. Both methods lead to comparable results. In the study a particular emphasis has been laid on investigations of the atomic core electrons (1s, 2s, 3s) and of the conduction electrons 4s on the Bf and IS values. The calculated values of the dIS/dlnV and dlnB /dlnV parameters give evidence of good conformity with those derived from experimental data.
Structural, electronic and thermal properties of Zn1−x MgxS ternary alloys are studied by using the full potential-linearized augmented plane wave method (FP-LAPW) within the density functional theory (DFT). The Wu-Cohen generalized gradient approximation (WC-GGA) is used in this approach for the exchangecorrelation potential. Moreover, the modified Becke-Johnson approximation (mBJ) is adopted for band structure calculations. The dependence of the lattice constant, bulk modulus and band gap on the composition x showed that the first exhibits a small deviation from the Vegard’s law, whereas, a marginal deviation of the second from linear concentration dependence (LCD). The bowing of the fundamental gap versus composition predicted by our calculations agrees well with the available theoretical data. The microscopic origins of the gap bowing are explained by using the approach of Zunger and co-workers. Thermal effects on some macroscopic properties of Zn1−x MgxS alloys are also investigated using the quasi-harmonic Debye model, in which the phononic effects are considered. As, this is the first quantitative theoretical prediction of the thermal properties of Zn1−x MgxS alloys, no other calculated results and furthermore no experimental studies are available for comparison.
Structural, elastic and thermodynamic properties of sodium chalcogenides (Na2X, X = S, Se) have been calculated using FP-APW+lo method. The ground state lattice parameter, bulk moduli have been obtained. The Zener anisotropy factor, Poisson’s ratio, shear modulus, Young’s modulus, have also been calculated. The calculated structural and elastic constants are in good agreement with the available data. We also determined the thermodynamic properties, such as heat capacities Cv and Cp, thermal expansion α, entropy S, and Debye temperature ΘD, at various pressures and temperatures for Na2X compounds. The elastic constants under high pressure and temperature are also calculated and elaborated.
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