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Creators/Authors contains: "Sundararaman, Siddharth"

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  1. Abstract

    Oxide glass, one of the most transformative materials in the modern world, breaks easily under load due to its brittleness. Using classical molecular dynamics simulations, we prepared amorphous alumina by consolidating glass nanoparticles at room temperature. We showed that consolidated amorphous alumina exhibits work hardening ability, hence deforms homogeneously and fractures via necking under tension, while amorphous alumina obtained from the traditional melt‐quench process fractures catastrophically due to severe shear banding. This finding suggests that if processed properly, amorphous oxides could deform and fracture like ductile metals, which will significantly expand the applications of oxide glasses into new areas where load bearing or mechanical reliability is necessary.

  2. Abstract

    Silica, sharing the same tetrahedral order and many structural, thermodynamic and dynamic anomalies with water, has been speculated to have a density increase upon melting similar to water. In this work, an increase in density upon melting cristobalite silica and a shallow density maximum followed by a density minimum during cooling of silica liquid are observed in classical molecular dynamics simulations. The density maximum gradually diminishes with the increase in alkali size/content in alkali silicate glasses. The structural origin of the anomalous density maximum in silica is revealed by detailed structural analysis. During the cooling process, a range of rings with different sizes form in liquid silica, with 6‐member rings being the most dominant, which cause the silica network to open up and compensate the regular volume shrinkage upon cooling. These two competing factors lead to a density maximum, but to a less extent than that observed in melting of cristobalite silica. With the increase in modifier size/content in the alkali silicate glasses, the connectivity of silica network gradually breaks down; the population of 6‐member rings decrease with the increase in smaller or larger rings, therefore the density maximum becomes less obvious and eventually disappears.