Regensburg 2004 – wissenschaftliches Programm

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DY: Dynamik und Statistische Physik

DY 46: Poster

DY 46.98: Poster

Donnerstag, 11. März 2004, 16:00–18:00, Poster D

First-principle investigations of phonon spectra of crystalline ice — •Waheed Adeniyi Adeagbo¹, Peter Entel ¹ und Jürgen Hafner² — ¹Institute of Physics, University of Duisburg-Essen, 47048 Duisburg, Germany. — ²Material Physics Institute, University of Vienna, Austria

Lattice dynamical calculations have been carried out for a tetrahedrally coordinated crystalline ice structure using Vienna Ab-initio Simulation Package (VASP). A one directional periodically replicated unit cell containing 24 molecules of water, whose constituents molecules are arranged according to Bernal-Fowler ice rules is employed in our phonon calculations. Dynamical properties were determined within the harmonic approximations by finite difference evaluation of the dynamical matrix from atomic forces. We investigated the effect of polarization arising from dipole-dipole interactions on our phonon spectra by carrying out two separate calculations with and without effect of induced polarization. The polariazation was taken into account by switching on the evaluation of the usual Berry phase expression for the electronic polarization of an insulating ground state system in the VASP code. This produces a significant effect in the splitting of longitudinal and transverse optic modes. Our results are discussed with respect to the neutron diffraction scattering data.