  A global hybrid extension of variational two-electron reduced-density matrix
(v2RDM)-driven multiconfiguration pair-density functional theory (MCPDFT) is
developed. Using a linear decomposition of the electron-electron repulsion
term, a fraction {\lambda} of the nonlocal exchange interaction, obtained from
v2RDM-driven complete active-space self-consistent field (CASSCF) theory, is
combined with its local counterpart, obtained from an on-top pair-density
functional. The resulting scheme (called {\lambda}-MCPDFT) inherits the
benefits of MCPDFT (e.g., its simplicity and the resolution of the symmetry
dilemma), and, when combined with the v2RDM approach to CASSCF,
{\lambda}-MCPDFT requires only polynomially scaling computational effort. As a
result, it can efficiently describe static and dynamical correlation effects in
strongly correlated systems. The efficacy of the approach is assessed for
several challenging multiconfigurational problems, including the dissociation
of molecular nitrogen, the double dissociation of a water molecule, and the
1,3-dipolar cycloadditions of ozone to ethylene and ozone to acetylene in the
O3ADD6 benchmark set.
