# Local Hybrid QM/QM Calculations of Reaction Pathways in Metallobiosites

journal contribution

posted on 09.12.2014, 00:00 by Milica Andrejić, Ricardo A. MataThe accurate calculation
of activation barriers is fundamental
for the modeling of reaction pathways. However, the computational
cost of describing electronic correlation at metal sites can be a
deterrent. A possible solution to this problem is the use of hybrid
QM/QM approaches, which combine different levels of theory in a single
calculation. In this way, the metal and its direct vicinity can be
treated, for example, with a coupled cluster method, with the remaining
system at the MP2 level. We present calculations on two selected molybdenum
complexes modeling the active sites of sulfite oxidase and dimethyl
sulfoxide reductase. Use is made of the LMOMO scheme, a hybrid QM/QM
model that enables the partition of the system directly at the orbital
level, thus avoiding the use of model systems. The results show that
even when the high-level calculations are restricted to the orbitals
directly located at the metal atom, most of the electronic correlation
effects are captured.