Ab initio diagnosis of isomerization pathway of diphosphene and diphosphinylidene

An appositeness of recently developed multireference perturbation theory coupled with an improved virtual orbitals complete active space configuration interaction reference function (IVO-SSMRPT) has been examined here against strongly correlated molecular systems emerging from isomerization of diphosphene and diphosphinylidene. The IVO-SSMRPT is an interesting alternative to the widely used MRPT methods which avoid some of the objections of the conventional MRPTs. IVO-BWMRPT furnish a reliable description of near-degeneracy between occupied and unoccupied orbitals at the twisted geometry where the wave function receives biradical character. Overall, the IVO-SSMRPT results are in good agreement with the more expensive state-of-the-art ab initio calculations discloses the accomplishment of the IVO-SSMRPT method. The IVO-SSMRPT method can be considered as an economical MR ab initio protocol that renders a good compromise between accuracy and computational expense.