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We report frozen-phonon local-density calculations for YBa2Cu3O7 of the infrared- and Raman-active apical-oxygen phonons in the c-direction. No sign of the suggested bistability or anharmonicity is found.

A first-principles prediction of the q dependence of the electronic susceptibility of YBa2Cu3O7 and the relation to experimentally observed phonon anomalies is presented.

Based on a numerically highly accurate local-density-approximation (LDA) calculation, we present a k\ensuremath{\cdot}p analysis of the interband optical absorption in ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ in the infrared region (\ensuremath{\Elzxh}\ensuremath{\omega}0.1 eV). It is shown that the LDA band structure gives rise to three infrared interband transitions: A sharp peak for the in-plane (E\ensuremath{\perp}c) polarization at about 320 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, a wide maximum for E\ensuremath{\parallel}c at about 420 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, and a structureless absorption (${\mathrm{\ensuremath{\epsilon}}}_{2}$\ensuremath{\approxeq}const) for E\ensuremath{\parallel}c. The first feature is due to transitions between the apical-oxygen-derived bands, the second one to that between the z-even and z-odd ${\mathrm{CuO}}_{2}$ plane bands, and the third one to the transitions between the chain band and the z-odd plane band. The possibility of observing these features in experiment is discussed.

We have calculated the renormalization of the specific heat in the normal state and the specific heat jump at Tc, using a realistic Eliashberg function, extracted from tunneling spectroscopy. The magnitude of the Eliashberg function was scaled so as to have the total coupling constant λ from 1.5 to 2.5. Using these calculations, we have analyzed recent measurements of the specific heat and have found that they can be reconciled with the band structure calculations, if λ≈2.

The FexCo1−xS2 system is predicted, on the basis of density functional calculations, to be a half metal for a wide concentration range. Unlike most known half metals, the half metalicity in this system is expected to be very stable with respect to crystallographic disorder and other types of defects.

{ital Ab} {ital initio} frozen-phonon calculations were performed for YBa{sub 2}Cu{sub 3}O{sub 7} for the five {ital A}{sub {ital g}} Raman-active and for two {ital B}{sub 1{ital u}} infrared-active optical {bold q}={bold 0} modes, with use of the local-density approximation and the full-potential linear-muffin-tin-orbital method. The full {ital A}{sub {ital g}} dynamical matrix was calculated using 98 {bold k} points in the 1/8 Brillouin zone. The theoretical and experimental equilibrium structures and phonon frequencies {omega}{sub {nu}} agree well. Phonon linewidths {gamma}{sub {nu}{bold q}}, due to electronic intraband transitions in the normal state, and electron-phonon coupling constants {lambda}{sub {nu}{bold q}}{identical to}{gamma}{sub {nu}{bold q}}/({pi}{ital N}(0){omega}{sub {nu}}{sup 2}) were calculated for the {ital A}{sub {ital g}} modes and small, transverse {bold q}. We estimate that {lambda}{approx}1 for the sum over all modes. The phonon shifts and broadenings observed for {ital T}{lt}{Tc} by Raman scattering are well accounted for by conventional strong-coupling theory and our calculated electron-phonon coupling.

The Hopfield factor (electronic part of the electron-phonon coupling constant) is calculated in the rigid-muffin-tin approximation (RMTA) for several perovskite high-{Tc} superconductors. Calculations were performed in the conventional spherical'' approximation and take into account the proper local symmetry. It is shown that the layered perovskite crystal symmetry generally favors strong electron-phonon interaction on the copper sites. We also estimate some non-RMTA effects.

The electronic structures of NiMnSb and CrO2 were calculated using a spin-polarised scalar relativistic linear muffin-tin orbital (LMTO) method. The self-consistent calculations were performed for the observed experimental lattice constants. Cubic NiMnSb (MgAgAs-type structure) and rutile-structure CrO2 are found to be 'half-metallic ferromagnets', i.e. they have a semiconducting gap in the minority-spin bands but metallic majority-spin bands. The calculated magnetic moments in both compounds were found to be in good agreement with the experimental values. The possibility of metastable magnetic states is investigated via extended Stoner factor calculations. It is shown that the position of the Fermi level with respect to the bandgap is extremely sensitive to the exchange-correlation potential approximation.

Recent data on the single-domain resistivity of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ are analyzed using the local-density-approximation calculations of the plasma frequencies and Fermi velocities. It is shown that the transport coupling constants ${\ensuremath{\lambda}}_{\mathit{t}\mathit{r}}$ for all three directions come out to be of the same order, namely about 1.5. The corresponding mean free path l=11 A\r{} at T=300 K, which dispels the popular notion that the local-density-approximation band structure yields unreasonably large \ensuremath{\lambda} and small l values. The possibility of an anisotropy in ${\ensuremath{\lambda}}_{\mathit{t}\mathit{r}}$ and of a difference between \ensuremath{\lambda} and ${\ensuremath{\lambda}}_{\mathit{t}\mathit{r}}$ is discussed with the help of results from rigid-muffin-tin calculations of the Hopfield factors \ensuremath{\eta}.

A simple technique for calculating the phonon-limited resistivity ( rho ph) of metals is described which is analogous to the Gaspari-Gyorffy method (1972) for calculating the electron-phonon coupling constant ( lambda ), rho ph and lambda are calculated for all 4d metals and silver. The HCP metals have been treated as cubic, as is common in calculations of lambda . For rho ph, however, this approach turns out to be too rough because it depends strongly on the average Fermi velocity which is very sensitive to crystal structure. In all transition metals investigated the superconducting and transport electron-phonon coupling constants are nearly equal, lambda approximately= lambda tr. Also nearly equal are their electronic parts, eta approximately= eta tr. The only exception is Pd, where eta tr is nearly 1.5 times larger than eta ; this is because the superconducting and transport properties of Pd are defined by different parts of the Fermi surface. Palladium is the only 4d metal where the Mott model of conductivity (s-d scattering) is valid.

In our paper we have presented an effective self-consistent procedure which has been applied to the calculation of the electronic structure of copper. The results attest to the high stability of this procedure. The method of previously attaining atomic self-consistency makes possible a substantial reduction of the volume of band-structure calculations and, therefore, of the total time of the SC procedure. It has thus become possible to carry out calculations with good accuracy for a number of physical properties and the binding energy of metals on medium-sized computers. It must be pointed out that the self-consistent calculation of the band structure with prior attainment of atomic self-consistency is also possible in other methods of constructing the band structure.

The authors have calculated the optical properties (dielectric function, reflectivity and electron energy loss function) of 15 metals, including all the 4d series, some 3d metals and some noble and simple metals. The calculations are based on the LMTO band structure with optical matrix elements. The very good quantitative agreement with optical measurements provides an a posteriori justification of the use of local density functional method in the calculations of the dynamical response in metals and also allows an analysis of the general trends in optical properties from the electronic structure point of view.

The Hopfield factor (electronic part of the electron-phonon coupling constant) is calculated in the Rigid-Muffin-Tin approximation (RMTA) for several perovskite high-T c superconductors. Calculations were performed in the conventional “spherical” approximation, as well as taking into account proper local symmetry. It is shown that the layered perovskite crystal symmetry generally favors strong electron-phonon interaction on copper site. We also estimate some for non-RMTA effects.