  We present an interface of the wavefunction-based quantum-chemical software
CFOUR to the multiscale modeling framework MiMiC. Electrostatic embedding of
the quantummechanical (QM) part is achieved by analytic evaluation of
one-electron integrals in CFOUR, while the rest of the QM/MM operations are
treated according to the previous MiMiC-based QM/MM implementation. Long-range
electrostatic interactions are treated by a multipole expansion of the
potential from the QM electron density to reduce the computational cost without
loss of accuracy. Testing on model water/water systems, we verified that the
CFOUR interface to MiMiC is robust, guaranteeing fast convergence of the SCF
cycles and optimal conservation of the energy during the integration of the
equations of motion. Finally, we verified that the CFOUR interface to MiMiC is
compatible with the use of a QM/QM multiple time-step algorithm, which
effectively reduces the cost of AIMD or QM/MM-MD simulations using higher level
wavefunction-based approaches compared to cheaper density-functional theory
based ones. The new wavefunction-based AIMD and QM/MM-MD implementation was
tested and validated for a large number of wavefunction approaches, including
Hartree-Fock and post-Hartree-Fock methods like Moller-Plesset, coupled
cluster, and complete active space self-consistent field.
