The concept of stress in a continuum body is well known, which is Cauchy stress, defined as the average amount of force exerted per unit area. In MD simulation virial stress is generally used as a equivalent of the continuum Cauchy stress. Of course we can get the stress tensor of per atom according to the Virial theory, but the problem is what is the meaning of the stress in the strain-stress curve of nanowire. How to calculate this stress? Is it still σ＝F/A? Have anyone had such good experience? Any guiding would be greatly appreciated. Thanks