Supercomputer simulations show that at the atomic level, material stress doesn't behave symmetrically. Widely-used atomic stress formulae significantly underestimate stress near stress concentrators such as dislocation core, crack tip, or interface, in a material under deformation. Supercomputers simulate force interactions of Lennard-Jones perfect single crystal of 240,000 atoms. Study findings could help scientists design new materials such as glass or metal that doesn't ice up.