The Many-body Expansion (MBE), which decomposes the energy of a system into a series of n-body terms that may be evaluated independently, has facilitated the study of substantially larger systems at the <i>ab initio</i> level than would be possible using the conventional methods of electronic structure theory. Methods based on the MBE are highly parallelizable and can be made to scale linearly with the size of the system under study. Still, the trade off in accuracy and scalability that is apparent at even the lowest levels of the MBE, and uncertainties arising from the finite precision of the underlying computations, limits the scope of systems that can be accurately studied.<br/> <br/>              In order to extend the system sizes that can be investigated using MBE-based methods, we have developed a Multilevel Many-body Expansion (MMBE) that can be applied in any MBE-based fragmentation method. This formulation of the MBE offers improved scalability, reduced error propagation, and greater insight into the n-body origins of various inter-fragment interactions. The applicability of the MMBE is demonstrated in a variety of fragment-based methods and model systems.

Multilevel many-body expansion for fragment-based methods

255th National Meeting (2018)

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