Hi Murali & Steve,
I’ve spent a good part of my professional career trying to answer this question. For the atomic stress calculated from the virial expression, one does indeed get a stress field qualitatively similar to a classic crack tip stress field. This has been shown by several authors in the literature, I suggest looking up articles by Abraham, Marder, Farkas and X. Zhou (just off the top of my head). I myself have done a few studies looking at crack tip stress fields, and a picture of one (for an MD simulation using lammps’ predecessor code ParaDyn) is attached below:
There are a few known issues with the atomic stress as compared with a continuum measure of stress. First, as one would expect the stress field is not singular as one approaches the crack tip. Rather, it reaches a finite maximum reflective of the non-local nature of the inter-atomic potential. Second, the behavior of the stress field is ill-defined near free surfaces (as noticed by Cheung & Yip and Zimmerman et al). Thus, recent publications from various authors (Hardy, Cormier et al., M. Zhou, Murdoch) have defined continuum measures of stress that can be extracted from atomistic quantities of force, position and velocity. These expressions are similar to, but differ from, the virial/atomic expression.