  The combination of density functional theory (DFT) with a
multiconfigurational wave function is an efficient way to include dynamical
correlation in calculations with multiconfiguration self-consistent field wave
functions. These methods can potentially be employed to elucidate reaction
mechanisms in bio-inorganic chemistry, where many other methods become either
too computationally expensive or too inaccurate. In this paper, a complete
active space (CAS) short-range DFT (CAS-srDFT) hybrid was employed to
investigate a bio-inorganic system, namely H2 binding to the active site of
[NiFe] hydrogenase. This system was previously investigated with
coupled-cluster (CC) and multiconfigurational methods in form of
cumulant-approximated second-order perturbation theory, based on the density
matrix renormalization group (DMRG). We find that it is more favorable for H2
to bind to Ni than to Fe, in agreement with previous CC and DMRG calculations.
The accuracy of CAS-srDFT is comparable to both CC and DMRG, despite that much
smaller active spaces were employed. This enhanced efficiency at smaller active
spaces shows that CAS-srDFT can become a useful method for bio-inorganic
chemistry.
