Theoretical calculations of the pressure effect for the β-phase of p-NPNN

Hybrid DFT (HDFT) calculations were carried out for model clusters of paranitrophenyl nitronyl nitroxide (p-NPNN) whose geometrical structures were based on its β-phase crystal structure. The effective exchange integrals between the neighboring p-NPNN molecules were calculated for the qualitative understanding of the pressure-induced transition form ferro- to antiferro-magnetic state.