Wavefunction-based electrostatic-embedding QM/MM using CFOUR through MiMiC

TL;DR

This paper introduces a new interface connecting CFOUR with MiMiC for wavefunction-based QM/MM simulations, enabling efficient and accurate long-range electrostatic calculations and compatibility with multiple time-step algorithms.

Contribution

The work develops a robust CFOUR-MiMiC interface that supports wavefunction-based methods and long-range electrostatics, enhancing the efficiency of high-level QM/MM molecular dynamics.

Findings

Verified robustness and energy conservation in water systems

Demonstrated compatibility with multiple wavefunction methods

Reduced computational cost with multiple time-step algorithms

Abstract

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.