DFT studies with local basis sets for solids: origin of the electronic instability in alpha-phases and electronic structure of metallic Zintl phases

Prof E Canadell,
Université de Barcelone, Espagne

Lundi 27 juin 2005, 11^h00, salle 2/3, Bâtiment St.Raphael, 3 rue Galilée, 94200 Ivry-sur-Seine
Density functional type calculations using numerical atomic orbitals basis sets will be used to discuss the relationship between the crystal and electronic structures of several low-dimensional materials and Zintl phases. The use of localized basis sets makes easier the discussion of the results in terms familiar for chemists.

Two different problems will be considered. We will first discuss the origin of the low-temperature resistivity anomaly in the molecular metal alpha-(BEDT-TTF)₂[KHg(SCN)₄] on the basis of the calculated Fermi surface and Lindhard response function. The results will be compared with recent X-ray diffuse scattering and magnetoresistance studies. The origin of the Fermi surface which contains both one-dimensional and two-dimensional contributions will be analyzed.

Then, the electronic structure of several recently reported metallic Zintl phases will be considered. The relationship between electron count and crystal structure and the relationship with the transport properties of phases like K₅Bi₄, K₃Bi₂, Ba₅In₄Bi₅, the origin of the unexpected metallic behaviour or the well known CaAl₂Si₂ phase, as well as the origin of the absence of a Peierls distortion in Li₂Ga will be discussed.