title: Impact of pressure on plastic yield in amorphous solids with open structure.
abstract: Plasticity in amorphous silica is unusual: The yield stress decreases with hydrostatic pressure, in contrast to the Mohr-Coulomb response commonly found in more compact materials such as bulk metallic glasses. To better understand this response, we have carried out molecular dynamics simulations of plastic response in a model glass with open structure. The simulations reproduce the anomalous dependence of yield stress with pressure and also correctly predict that the plastic response turns to normal once the material has been fully compacted. We also show that the overall shape of the yield surface is consistent with a quadratic behavior predicted assuming local buckling of the structure, a point of view that fits well into the present understanding of the deformation mechanisms of amorphous silica. The results also confirm that free volume is an adequate internal variable for a continuum scale description of the plastic response of amorphous silica. Finally, we also investigate the long-range correlations between rearrangement events. We find that strong intermittency is observed when the structure remains open, while compaction results in more homogeneous rearrangements. These findings are in agreement with recent results on the effect of compression on the middle range order in silicate glasses and also suggest that the well-known volume recovery of densified silica at relatively low temperatures is in fact a form of aging.
authors.affiliation: Laboratoire de Physique Théorique de la Matière Condensée, Paris Sorbonne Universités UPMC, BP 121, 4 Place Jussieu, 75252 Paris Cedex 05, France.
authors.forename: B
authors.initials: B
authors.lastname: Mantisi
authors.affiliation: Materials Sciences and Structures Division, Ecole des Mines de Saint-Etienne, LGF UMR No. 5307, CNRS, 158 Cours Fauriel, 42023 Saint-Etienne Cedex 2, France.
authors.forename: G
authors.initials: G
authors.lastname: Kermouche
authors.affiliation: École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris ParisTech, PSL Research University, Sciences et Ingénierie de la matière Molle, CNRS UMR No. 7615, 10 Rue Vauquelin, F-75231 Paris Cedex 05, France and Sorbonne-Universités, UPMC Université Paris 06, SIMM, 10 Rue Vauquelin, 75231 Paris Cedex 05, France.
authors.forename: E
authors.initials: E
authors.lastname: Barthel
authors.affiliation: Université de Lyon, LaMCoS, INSA-Lyon, CNRS UMR5259, F-69621, France.
authors.forename: A
authors.initials: A
authors.lastname: Tanguy