Band-structure Examination By The Lmto Method

The band structure regarding the fluorite-type -Bi2O3was calculated by the linear LMTO methods within the approximation of overlapping atomic spheres creating use of the basis set of orthogonal orbitals LMTO-ASA and by the full-potential LMTO method LMTO-FP for 3 vacancy orientations over a large section of oxygen concentrations. The calculated parameters of chemical bondsthe binding life Ebin and the compression regarding the electron-nuclear systemshow that the greatest stable compound is that with 3 vacancies per unit cell, oriented predominantly along the 111 direction. The hybrid BiO bonds are weak, and mostly the BiBi bonds are responsible for the structural stabilization of -Bi2O3. The mechanism regarding the formation of a semiconductor gap within the band structure of -Bi2O3 is discussed. Because regarding the variational character regarding the greatest regarding the modern band structure calculation methods, within LMTO, the calculated electron energies are many more accurate than the wave functions.

This affects greatly the optical matrix elements calculations. We investigated the challenge regarding the accurate calculation regarding the matrix elements within the frameworks of usual band structure methods, basing on the continuity equation for the charge density operator. We have derived an analytical expression for corrections to the common-used formulas for the optical matrix elements. These let to compute the matrix elements together with the similar to accuracy as the band structure such that the intraband matrix elements are exactly equal to the band electron velocities. A critical prescription is proposed for the optical matrix elements calculation within the frameworks regarding the LMTO method.

The imagine components regarding the dielectric functions are calculated for Cu and Pd within the life section 0. 120 eV, which agree well with available experimental data. Full-Potential Linear Muffin-Tin Orbital FP-LMTO Method. The full-potential linear muffin-tin orbital FP-LMTO method is a critical implementation of density functional theory within the regional density approximation LDA. In this method there is no shape approximation to the crystal potential, unlike methods based on the atomic-spheres approximation ASA where the potential is assumed to be spherically symmetric around each atom.

For mathematical convenience the crystal is divided up into regions inside muffin-tin spheres, where Schrdinger's equation is solved numerically, and an interstitial region. In all LMTO methods the wavefunctions within the interstitial region are Hankel functions.