Abstract: We develop a static quantum embedding scheme that utilizes different levels of approximations to coupled cluster (CC) theory for an active fragment region and its environment. In this approach, we solve the local fragment problem using a high-level CC method and address the environment problem with a lower-level Møller–Plesset (MP) perturbative method combined with an efficient relaxation mechanism. We define a static renormalized interaction for the fragment problem with the quantities obtained from the low-level method. This method has been assessed for convergence with respect to the basis set size, fragment size, and other parameters. We have analyzed the symmetry breaking issues arising upon bond stretching of a molecule when unrestricted references are used. Various enhancements of the method including multi-fragment calculations and the use of higher rank cluster operators will also be Discussed.
Bio: Avijit Shee is an Assistant Project Scientist with Birgitta Whaley, Lin Lin and Martin Head- Gordon at University of California, Berkeley. He works on Quantum embedding method (Green’s function-based and wave function-based first principle quantum dynamics method based on selected CI.
