The lattice instabilities of perovskite structure oxides are responsible for many of their interesting properties, such as temperature-dependent ferroelectric phase transitions. First-principles calculations using linear response theory provide an accurate means to determine the lattice dynamics throughout the entire Brillouin zone (BZ). Using the LAPW linear response method [1], we have previo...

Extensive LAPW frozen phonon calculations were performed in order to understand the origin of ferroelectricity in LiTaO3 and LiNbO3. Displacement of the Li atoms alone results in an anharmonic single well, whereas displacements of oxygen and lithium together result in deep double wells, much deeper than the transition temperatures, TC . This is contrary to current theories which model the under...

The structural, electronic and magnetic properties of Fe bulk and the monatomic Fe-nano wire has been theoretically investigated within the full potential linearized augmented plane wave (FP-LAPW) based on density functional theory (DFT). This work is a comparative study of Fe-bulk and the 1D Fe chain. A most commonly adopted GGA approximation is use for electron exchange correlation. In our ca...

I have carried out numerical first principles calculations of the pressure dependence of the elastic moduli for several ordered structures in the Aluminum-Lithium system, specifically FCC Al, FCC and BCC Li, L12 Al3Li, and an ordered FCC Al7Li supercell. The calculations were performed using the full potential linear augmented plane wave method (LAPW) to calculate the total energy as a function...

(19)F isotropic chemical shifts for alkali, alkaline earth and rare earth of column 3 basic fluorides are measured and the corresponding isotropic chemical shieldings are calculated using the GIPAW method. When using the PBE exchange-correlation functional for the treatment of the cationic localized empty orbitals of Ca(2+), Sc(3+) (3d) and La(3+) (4f), a correction is needed to accurately calc...

We report the results of the electronic structure calculation of a newly discovered member of the YBCO high-Tc family, i.e., Y3Ba5Cu8O18 (Y358) with Tc > 100, based on the full-potential linearized augmented plane waves method (FP-LAPW) of density functional theory in the generalized gradient approximation (GGA). The evolution of the number of hole carriers in different sites of the CuO2 planes...

We develop a many-body force field (FF) for tantalum based on extensive ab initio quantum mechanical (QM) calculations and illustrate its application with molecular dynamics (MD). As input data to the FF we use ab initio methods (LAPW-GGA) to calculate: (i) the zero temperature equation of state (EOS) of Ta for bcc, fcc, and hcp crystal structures for pressures up to ∼500 GPa, and (ii) elastic ...

The “Standard Model” of the Electronic Structure of Dots Progress made in the growth of “freestanding” (e.g., colloidal) quantum dotslt2 (see also articles in this issue by Nozik and MiCi6, and by Alivisatos) and in the growth of semiconductor-embedded (“self-assembled”) dots3p4 (see also the article by Bimberg, Grundmann, and Ledentsov in this issue) has opened the door to new and exciting spe...

This paper investigated the structural, optical, electronic and thermal characteristics of SrSnO3 perovskites that were calculated using density functional theory. Software called WEIN2K is used to perform calculation. According our calculations, band gap energy roughly 4.00 eV it adopts a distorted cubic shape in space group Pm3-m. The structure partial state reflects major contribution O 2p v...