Requests for technical support from the VASP group should be posted in the VASP-forum.

PSTRESS

If the PSTRESS tag is specified VASP will add this stress to the stress tensor, and an energy ${\displaystyle E=V*{\mathrm {PSTRESS}}}$ to the energy. This allows the user to converge to a specified external pressure. Before using this tag please read the section Energy vs volume Volume relaxations and Pulay stress