Interfacing Q-Chem and CHARMM to perform QM/MM reaction path calculations

Abstract: A hybrid quantum mechanical/molecular mechanical (QM/MM) potential energy function with HartreeFock, density functional theory (DFT), and post-HF (RIMP2, MP2, CCSD) capability has been implemented in the CHARMM and Q-Chem software packages. In addition, we have modified CHARMM and Q-Chem to take advantage of the newly introduced replica path and the nudged elastic band methods, which are powerful techniques for studying reaction pathways in a highly parallel (i.e., parallel/parallel) fashion, with each pathway point being distributed to a different node of a large cluster. To test our implementation, a series of systems were studied and comparisons were made to both full QM calculations and previous QM/MM studies and experiments. For instance, the differences between HF, DFT, MP2, and CCSD QM/MM calculations of H2O· · · H2O, H2O· · · Na+ , and H2O· · · Cl− complexes have been explored. Furthermore, the recently implemented polarizable Drude water model was used to...

• Type: Journal
• Year: 2007
• Where: JCC
• Authors: H. Lee Woodcock III, Milan Hodoscek, Andrew T. B. Gilbert, Peter M. W. Gill, Henry F. Schaefer III, Bernard R. Brooks
• Keywords: CHARMM, JCC 2007, Q-Chem, Q-Chem Software Packages