Medium-range order in alkali metaphosphate glasses and melts investigated by reverse Monte Carlo simulations and diffraction analysis.

Sylvie Beaufils (1) , Laurent Cormier (2) , Monica Bionducci (3) , Claude Ecolivet (1) , Georges Calas (2) , André Le Sauze (4) , Roger Marchand (5)

1 GMCM - Groupe matière condensée et matériaux
2 IMPMC - Institut de minéralogie et de physique des milieux condensés
3 LLB - UMR 12 - Laboratoire Léon Brillouin
4 ISCR - Institut des Sciences Chimiques de Rennes
5 Laboratoire Verres et Céramiques

Reverse Monte Carlo simulations have been performed on the alkali metaphosphate glasses Na0.5Li0.5PO3 and LiPO3 concerning structural experimental data obtained by neutron and x-ray diffraction at 300 K for both systems and versus temperature up to the melting point for the mixed composition. It appears that the contrast effect due to the negative scattering length of Li is not the only reason for the difference in the intensity of the prepeak observed in both systems. The main structural difference lies in the intermediate-range order, while the short-range order is quite similar in both systems. Moreover, it is shown that the intensity increase of the prepeak in the Na0.5Li0.5PO3 structure factor is due to the partial structure factors of the PO4 tetrahedron, sustaining the hypothesis of an ordering between several PO4 tetrahedra and voids with temperature.

Mots clés: sodium compounds; lithium compounds; phosphate glasses; glass structure; Monte Carlo methods; neutron diffraction; X-ray diffraction; noncrystalline defects; liquid structure

Sylvie Beaufils, Laurent Cormier, Monica Bionducci, Claude Ecolivet, Georges Calas, et al.. Medium-range order in alkali metaphosphate glasses and melts investigated by reverse Monte Carlo simulations and diffraction analysis.. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2003, 67, pp.104201 (1-7). ⟨10.1103/PhysRevB.67.104201⟩. ⟨hal-00085080⟩