title: Topologically ordered amorphous silica obtained from the collapsed siliceous zeolite, silicalite-1-F: a step toward "perfect" glasses.
abstract: A dense amorphous form of silica was prepared at high pressure from the highly compressible, siliceous zeolite, silicalite-1-F. Reverse Monte Carlo modeling of total X-ray scattering data shows that the structure of this novel amorphous form of SiO(2) recovered under ambient conditions is distinct from vitreous SiO(2) and retains the basic framework topology (i.e., chemical bonds) of the starting crystalline zeolite. This material is, however, amorphous over the different length scales probed by Raman and X-ray scattering due to strong geometrical distortions. This is thus an example of new topologically ordered, amorphous material with a different intermediate-range structure, a lower entropy with respect to a standard glass, and distinct physical and mechanical properties, eventually approaching those of an "ordered" or "perfect" glass. The same process in more complex aluminosilicate zeolites will, in addition, lead to an amorphous material which conserves the framework topology and chemical order of the crystal. The large volume collapse in this material may also be of considerable interest for new applications in shock wave absorption.
authors.affiliation: Institut Charles Gerhardt Montpellier, Equipe PMOF, UMR 5253 CNRS-UM2-ENSCM-UM1, Universite Montpellier II, Sciences et Techniques du Languedoc, Place E. Bataillon cc1504, 34095 Montpellier Cedex 05, France. jhaines@lpmc.univ-montp2.fr
authors.forename: Julien
authors.initials: J
authors.lastname: Haines
authors.forename: Claire
authors.initials: C
authors.lastname: Levelut
authors.forename: Aude
authors.initials: A
authors.lastname: Isambert
authors.forename: Philippe
authors.initials: P
authors.lastname: Hébert
authors.forename: Shinji
authors.initials: S
authors.lastname: Kohara
authors.forename: David A
authors.initials: DA
authors.lastname: Keen
authors.forename: Tahar
authors.initials: T
authors.lastname: Hammouda
authors.forename: Denis
authors.initials: D
authors.lastname: Andrault