Temperature-dependent electronic structure: from heavy fermion behaviour to phase stability

The temperature (T)-dependent density functional approach and some methods for calculating bands in structurally disordered systems are described. The band results are used for determining thermodynamic properties. The methods are applied to determine T-dependent properties in systems which are sensitive to temperature as the result of special density-of-state features at the Fermi energy. Such systems include heavy fermion Ce-compounds, FeSi, and fcc Ce, and the properties are specific heat enhancements, large magnetic susceptibility, and the alpha-gamma transition, respectively. The phase stability of transition metals at high T are studied with the purpose of separating the electronic and vibrational effects. T-dependent effects in copper oxides leading to nonlinear electron-phonon coupling are discussed. Finally, calculations of momentum densities are shown to give a sensitive indication of thermal disorder in alkali metals. It is found that the effects of disorder are often similar to the effects of strong correlation.