Stress from electronic structure
The subject of this appendix is the macroscopic stress that enters mechanical properties of matter in the form of stress–strain relations. The stress tensor is the generalization of pressure to all the independent components of dilation and shear, and the “stress theorem” is the generalization of the virial theorem for scalar pressure to all components of the stress tensor. In condensed matter, the state of the system is specified by the forces on each atom and the stress, which is an independent variable. The conditions for equilibrium are: (1) that the total force vanishes on each atom, and (2) that the macroscopic stress equals the externally applied stress.
G.1 Macroscopic stress and ...