Crack nucleation criterion and its application to impact indentation in glasses.

Molecular dynamics (MD) simulations are used to directly observe nucleation of median cracks in oxide glasses under indentation. Indenters with sharp angles can nucleate median cracks in samples with no pre-existing flaws, while indenters with larger indenter angles cannot. Increasing the tip radius increases the critical load for nucleation of the median crack.

Importance of C(2) symmetry for the device performance of a newly synthesized family of fused-ring thiophenes.

We investigated the relationship between molecular structure and field-effect hole mobility in a family of fused-ring polythiophene copolymers that we designed recently. The results suggest that a repeat unit that possesses a C(2) axis perpendicular to the conjugation plane is important to achieve a high-mobility. Our finding is supported by a review of literature data: Many polymer semiconductors showing a hole or electron mobility >0.

Origin of dynamical heterogeneities in calcium aluminosilicate liquids.

We investigate the heterogeneous dynamics of calcium aluminosilicate liquids across both the peraluminous and peralkaline regimes. Using the isoconfigurational ensemble method we find a clear correlation between dynamical heterogeneities and concentration fluctuations. Regions of high dynamic propensity have higher concentrations of both calcium and aluminum, whereas low propensity regions are silica rich.