Electrostatic Interaction of the Electrostatic-Embedding and Mechanical-Embedding Schemes for QM/MM Calculations

Yan Zhang
2013 Communications in Computational Chemistry  
The geometries of the system including two waters have been optimized by the full quantum calculations with the constraints of the O-O distance. The HF and B3LYP density function levels with STO-3G, 6-31G, 6-31G*, and 6-31++G** four basis sets were used in the optimizations. At the optimized geometries, the QM/MM single point interaction energies of the electrostatic-embedding and mechanical-embedding schemes were calculated. The QM/MM interaction energies were compared with the full quantum
more » ... the full quantum calculations. The results reveal that the basis sets could be important in the QM/MM calculations. The QM/MM method of the two schemes could not accurately describe the energy of the structure. The electrostatic and VDW interaction energy between QM and MM regions of the electrostatic-embedding scheme is better than that of the mechanical-embedding scheme at the 6-31G and 6-31G* levels. At the 6-31++G** level, the energies of the two schemes are in good agreement with the full quantum calculations. Present investigation suggests that the electrostatic-embedding scheme could be more suitable in the QM/MM simulations of very large systems, e.g. emzyme reaction. The cutoff radius of the electrostatic-embedding scheme is at least 25a0.
doi:10.4208/cicc.2013.v1.n2.1 fatcat:jfcnhbqurrcczbqzqo7eslbsne