| 講演要旨： |
In this lecture we will elaborate on the modeling the structural responses of solids to thermal and mechanical loading to gain mechanistic understanding generally not available from experiments. Theoretical strength is defined through elastic modes of instability, or the onset of soft vibrational modes in the deformed lattice. In the kinetics of melting we distinguish between the thermoelastic process of mechanical melting which sets the upper limit of metastability, and the free-energy driven process of thermodynamic melting which involves defect nucleation and growth. By considering two single-crystal deformations separately, affine shear and nanoindentation, we uncover atomic-level details on the nucleation of dislocation and deformation twinning. To model the combined effects of stress and reactivity with water we determine the activation barrier for water-silica interaction in a stressed silica nanorod using reaction pathway sampling, as a first step towards a molecular description of hydrolytic weakening. Essentially the same approach allows us to elucidate the mechanism of crack-tip plasticity by determining the saddle-point configuration for the initial bowing out of a dislocation loop, a problem previously analyzed at the continuum level. |
