If a constant external pressure is applied to a solid material, once an equilibrium is achieved, the stress outside of the material must be balanced by the internal counterstress. The stress theorem devel-oped by Nielsen and Martin establishes a way to calculate the stress tensor induced by an externally applied pressure to a system in PBC simulations. It is closely related to the force theorem and the quantum mechanical virial theorem. In the stress theorem, the Hamiltonian of the system is considered as