Next week's seminar

[CM ICTP - Trieste]

								06/06

JOINT ICTP/SISSA CONDENSED MATTER SEMINARS
Academic Year 2005/06



SEMINAR ROOM - MAIN BUILDING   (first floor)



Tuesday, 12 September -     4:00 p.m.



V. ANISIMOV   ( Institute of Metal Physics, Ekaterinburg )



" Orbital densities functional "


Abstract

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 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 problem of metal insulator transition 
in lanthanum trihydride LaH{3-x}. In LDA calculations ground state of 
this 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}.
http://xxx.lanl.gov/abs/cond-mat/0602204