Veranstaltungsdetails

2.3.2006, 15:03
Jungiusstr. 9, Hörsaal III

SFB 668 - Kolloquium

Prof. Vladimir Anisimov (Univ. Ekaterinburg / ETH Zürich):

Orbital densities functional

Local density approximation (LDA) to density functional theory (DFT) has continuous derivative of total energy as a number of electrons function and continuous exchange-correlation potential, while in emph{exact} DFT both should be discontinuous as number of electrons goes through an integer value. We propose orbital densities functional (ODF) (with orbitals defined as Wannier functions) that by construction obeys this discontinuity condition. By its variation one-electron equations are obtained with potential in the form of projection operator. The operator increases a separation between occupied and empty bands thus curing LDA deficiency of energy gap value systematic underestimation. Orbital densities functional minimization gives ground state orbital and total electron densities. The ODF expression for energy of orbital densities fluctuations around the ground state values defines ODF fluctuation Hamiltonian that allows to treat correlation effects. Dynamical mean-field theory (DMFT) was used to solve this Hamiltonian with quantum Monte Carlo (QMC) method for effective impurity problem. We have applied ODF method to the problems of antiferromagnetic insulator NiO and metal insulator transition in lanthanum trihydride LaH(3-x). In LDA calculations ground state of the hydride material is metallic for all values of hydrogen non-stoichiometry x while experimentally the system is insulating for x<0.3. ODF method gave paramagnetic insulator solution for LaH3 and LaH{2.75} but metallic state for LaH{2.5}.