BIRS Workshop Lecture Videos

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BIRS Workshop Lecture Videos

Tensor decomposition and coupled cluster theory in the context of quantum molecular dynamics Christiansen, Ove


During the last decade we have developed coupled cluster based theoretical methods for calculating of vibrational wave functions, spectra and molecular properties. In this talk I will discuss tensor decomposition and it is use in achieving a concise representation of the wave functions for nuclear motion. In particular I will discuss the integration of the tensor decom- position idea in the context of vibrational coupled cluster (VCC) and vibrational configuration interaction (VCI) wave functions. I will outline the basic aspects of vibrational wave functions focusing and VCC and VCI and the importance of correlation amplitudes: the many small contributions that together make up the total wave function. I will take a tensor decomposition perspective on the relation between VCC and VCI. A pilot implementation has been made for the CANDECOMP/PARAFAC tensor decomposition within our existing VCC/VCI codes. Numerical studies on models systems, formaldehyde, and thiadiazole will be used to illustrate the theoretical concepts. The significance of size–extensivity in relation to screening away small contributions will also be discussed.

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