The structure of the first co-ordination shell of Pb atoms in lead - silicate glasses : a molecular dynamics study

• Autorzy: Rybicka A. , Rybicki J. , Witkowska A. , Feliziani S. , Mancini G.
• Języki publikacji: PL

Abstrakty

EN

The structure of lead-silicate glasses, although being investigated for over sixty years, rema ins still controversial. One of the open questions is the structure of the lead subsystem: what are the basic structural units like, and how are they interconnected. In the literature the appearance of [PbO4]n, or [PbO3]n chains is reported even in the glasses of the same stoichiometry. In order to elucidate the problem of contradicting experimental findings, extensive molecular dynamics (MD) simulations in the isobaric-isoenthalpic (NpH) ensemble of the structure of lead-silicate glasses have been performed in the whole range of glassformation. The atoms were assumed to interact by a two-body Born-Mayer-Huggins interaction potential with full ionic charges. The potential parametrization was taken from Damodaran et al. [Phys. Chem. Glasses, 31, 212 (1990)]. The simulation box contained about 3000 atoms. For each composition an equilibrated melt at 10000 K was prepared, and then slowly (6 ź 1013 K/s) cooled down to 300 K, passing several equilibrium states at intermediate temperatures. The simulation results can be summarised as follows. For 0.1 = x = 0.33, about ? of all Pb atoms is either placed in the front of the faces of the SiO 4 tetrahedra, forming PbO3 pyramids with the Pb atom in the vertices or in the middle of an almost flat triangle formed from apical oxygens of three different SiO 4 tetrahedra. Another ? of all Pb atoms can be qualified as vertices of rather distorted square pyramids. The remaining ? o f lead atoms have neighbourhoods difficult to classify. For x = 0.67 only a few Pb atoms were identified as remaining in the front of a face of a SiO 4 tetrahedron. Most of the Pb atoms are placed in the vertices of edge sharing square PbO4 pyramids. Our MD results are compared with available experimental data.

• Wydawca: Institute of Bioorganic Chemistry Scientific Publishers OWN, Polish Academy of Sciences
• Czasopismo: Computational Methods in Science and Technology
• Rocznik: 1999
• Tom: Vol. 5
• Strony: 67--74
• Opis fizyczny: Bibliogr. 28 poz., rys., tab.

Twórcy

autor

Rybicka A.

autor

Rybicki J.

autor

Witkowska A.

autor

Feliziani S.

autor

Mancini G.

• Department of Solid State Physics, Faculty of Technical Physics and Applied Mathematics, Technical University of Gdansk, Narutowicza 11/12, 80-952 Gdansk, Poland