where the first and second terms are kinetic energies of the nuclei and the Kohn-Sham orbitals, respectively. E KS is the potential energy of the QM subsystem computed at the level of density functional theory (DFT). E MM is the potential energy of the MM subsystem which is computed by using the GULP code. E QM/MM represents the interaction energy between QM and the MM subsystems, which consists of bonding, dispersion, and electrostatic energies. Both the bonding and the dispersion terms are computed at the MM level, whereas the electronic embedding scheme is employed for computing the electrostatic energy. The last term in Eq. 1 ensures that the orthonormality constraints are satisfied during the time evolution of the Kohn-Sham orbitals where Λ is Lagrange multiplier and summation goes over all the occupied orbitals.