Regensburg 2013 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 35: Computational Materials Modelling - Phonons & Phase Stability

MM 35.4: Vortrag

Mittwoch, 13. März 2013, 12:30–12:45, H24

Comparison of phonon frequencies and polarization vectors obtained from fitted force constants or from ab initio force constants — •Christian Illg¹, Bernd Meyer², and Manfred Fähnle¹ — ¹Max-Planck-Institut für Intelligente Systeme, 70569 Stuttgart, Germany — ²Interdisziplinäres Zentrum für Molekulare Materialien und Computer-Chemie-Centrum, Universität Erlangen-Nürnberg, 91052 Erlangen, Germany

The calculation of electron-phonon scattering matrix elements is necessary in many physical contexts and requires reliable information about phonon frequencies and polarization vectors. One can calculate the phonon frequencies and polarization vectors from the dynamical matrix which is the Fourier-transformed force-constant matrix. The force constants can either be determined by a fit to experimental data or by an ab initio calculation. It is well known that the fitted force constants cannot be determined unambiguously since the polarization vectors are hard to measure and do not enter the fit [1]. A unitary transformation would alter the force constants while leaving the frequencies unchanged (but the polarization vectors would change). We compare the frequencies and polarization vectors in the whole Brillouin zone obtained from fitted force constants and obtained from ab initio force constants [2]. The results are important to make a statement on the reliability of phonon polarization vectors obtained from fitted force constants.
R. S. Leigh, B. Szigeti, V. K. Tewary, Proc. R. Soc. London, Ser. A 320, 505 (1971)
C. Illg, B. Meyer, M. Fähnle, Phys. Rev. B 86, 174309 (2012)