The development of accurate and broadly applicable methods for large molecules continues to be a major challenge in quantum chemistry. We have recently developed a general fragment-based approach (M  olecules-I  n-M olecules, MIM) for the accurate evaluation of the energies of large molecules. In this method, we use a multilayer partitioning technique with multiple levels of theory using a generalized hybrid energy expression, similar in spirit to the ONIOM methodology. The accuracy of the method can be improved further using a novel two-body expansion approach involving overlapping subsystems. While the methods were initially targeted for the study of bonded systems, novel implementations on non-bonded systems have now been carried out.Our methods have excellent scaling as well as high accuracy and are useful tools for investigations on large molecular systems. Our theoretical approach as well as careful assessments from applications on peptides and large water clusters will be discussed.                                                                                  

Fragment-based methods for large molecular systems

246th National Meeting (2013)

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