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Session K24 - Theory of Materials: Linear and Nonlinear Dielectric Response.
MIXED session, Wednesday afternoon, March 20
Room 120, America's Center
Interest in the behavior of semiconducting or nearly semiconducting intermetallic compounds has been recently stimulated by their relevance to quasicrystals and materials for thermoelectric applications. For nearly semiconducting orthorhombic Al_2Ru, we present zone center optical phonon frequencies, Born effective charge and electronic dielectric tensors calculated using variational density functional perturbation theory with ab initio pseudopotentials and a plane wave basis set. The results are compared with the recent measurements on polycrystalline samples by D. Basov et al., which showed anomalously strong far IR absorption by optical phonons. The corresponding first-principles results are used to investigate the origin and implications of the dynamical effective charges for Al and Ru, and the connections to static charge transfer, bonding character, structural stability, and pseudogap formation in the electronic density of states at the Fermi level.