Regensburg 2013 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 39: Computational Materials Modelling - Transport, Excitations, Time Dependence I
MM 39.3: Vortrag
Mittwoch, 13. März 2013, 15:30–15:45, H24
Ab-initio study of q-dependent screening parameters and effective plasma frequencies in simple metals — •Steffen Kaltenborn and Hans Christian Schneider — University of Kaiserslautern, 67653 Kaiserslautern, Germany
We present results of an ab-initio study of the dielectric function ε(q,ω) in the RPA approximation together with energies and wave functions from density functional theory [1,2]. We have implemented the linear tetrahedron method for the computation of the dielectric function and therefore do not need to use a phenomenological broadening of the energy conserving delta function. From the dielectric function we determine the effective plasma frequency Ω and the static screening wave number κ for the simple metals aluminum, silver and copper. In all metals, we find a pronounced deviation from the parabolic dispersion Ω∝ q2 of the plasma frequency that is often assumed [3]. In particular, for aluminum the effective plasma frequency decreases with finite q-vectors until it reaches the electron-pair continuum. We also discuss the influence of the spin mixing on plasma frequency and screening wave number. Last, we compare our results with measurements [4] and with computed results using a finite broadening in the RPA dielectric function, as implemented in current DFT codes [1,2].
[1] DFT-Program Elk FP-LAPW Code, http://elk.sourceforge.net.
[2] C. Ambrosch-Draxl et al., Comp. Phys. Commun. 175, 1-14, (2006).
[3] G. Piazza et al., Solid State Commun. 51, 905-908, (1984).
[4] Ellen J. Zeman et al., J. Phys. Chem. 91, 634-643 (1987).