Systematic Fragmentation Method and the Effective Fragment Potential: An Efficient Method for Capturing Molecular Energies

TitleSystematic Fragmentation Method and the Effective Fragment Potential: An Efficient Method for Capturing Molecular Energies
Publication TypeJournal Article
Year of Publication2009
AuthorsMullin JM, Roskop LB, Pruitt SR, Collins MA, Gordon MS
Journal TitleJournal of Physical Chemistry A
Date Published09/17
ISBN Number1089-5639
Accession NumberISI:000269656000013
Keywordsab-initio calculation, consistent basis, coupled-cluster theory, density-functional theory, electron correlation methods, fast multipole method, gaussian-basis sets, periodic boundary-conditions, plesset perturbation-theory, quantum-mechanical calculation

The systematic fragmentation method fragments a large molecular system into smaller pieces, in such a way as to greatly reduce the computational cost while retaining nearly the accuracy of the parent ab initio electronic structure method. In order to attain the desired (sub-kcal/mol) accuracy, one must properly account for the nonbonded interactions between the separated fragments. Since, for a large molecular species, there can be a great many fragments and therefore a great many nonbonded interactions, computations of the nonbonded interactions can be very time-consuming. The present work explores the efficacy of employing the effective fragment potential (EFP) method to obtain the nonbonded interactions since the EFP method has been shown previously to capture nonbonded interactions with an accuracy that is often comparable to that of second-order perturbation theory. It is demonstrated that for nonbonded interactions that are not high on the repulsive wall (generally >2.7 angstrom), the EFP method appears to be a viable approach for evaluating the nonbonded interactions. The efficacy of the EFP method for this purpose is illustrated by comparing the method to ab initio methods for small water Clusters, the ZOVGAS molecule, retinal, and the a-helix. Using SFM with EFP for nonbonded interactions yields an error of 0.2 kcal/mol for the retinal cis-trans isomerization and a mean error of 1.0 kcal/mol for the isomerization energies of live small (120-170 atoms) alpha-helices.

URL<Go to ISI>://000269656000013