Dresden 2003 – wissenschaftliches Programm

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DY: Dynamik und Statistische Physik

DY 32: Glasses II (joined session FV DF/DY)

DY 32.8: Vortrag

Dienstag, 25. März 2003, 16:30–16:45, HSZ/403

Vibrational Dynamics of Phosphate Glasses: Ab-initio versus Classical Force Fields — •Nikolay Zotov¹ and Takashi Uchino² — ¹Mineralogical Institute, Uni Bonn, Poppelsdorfer Schlo(ß), D-53115 Bonn — ²Dep. Chemistry, Uni Kobe, Kobe 657-8501, Japan

Molecular-like clusters of Na, P and O atoms have been created by ab-initio molecular orbital calculations to model the vibrational spectra of sodium metaphosphate (NaPO3) glass. The geometry of the clusters was optimized at the Hartree-Fock level using different basis sets. The vibrational density of states is calculated both ab-initio and using a valence force field and is compared with neutron inelastic scattering data. The localization, phase quotient and local symmetry of the vibrational modes, calculated using both approaches, are in good agreement. Polarized Raman spectra are calculated both ab-initio and in the bond-polarizability approximation and are compared with experimental Raman spectra. The nature of the atomic interactions and the character of the vibrational modes in NaPO3 glass are discussed on the basis of the results obtained. The financial support of the DFG (SFB 408) is kindly acknowledged.