Speaker
Description
Capturing correlation effects in quantum many-body systems remains a major challenge in the physical description of molecules. Coupled cluster theory has proven to be very accurate in a weakly interacting, weakly correlated setting while scaling comparatively favourably with system size. However, it struggles with systems with large static correlations. This issue is known as the multi-reference problem as conventional coupled cluster approaches rely on a single Slater determinant as their reference state and struggle with systems that cannot adequately be approximated this way. Examples for such systems are molecules whose geometries differ from the equilibrium configuration, for instance molecules adsorbed to surfaces. The time-dependent two-particle reduced density matrix (TD2RDM) method has the same system size scaling as time-dependent extensions of coupled cluster singles doubles theory without relying on the choice of a reference state. Thus, it is a promising alternative for the description of molecules and other correlated systems with multi-reference character.
In this work, we present first results for the application of the TD2RDM method to small molecular systems. We compare results with coupled cluster theory, time-dependent Hartree Fock, as well as numerically exact calculations. In particular, we address the issue of robustness of these approaches with respect to the multi-reference character of the simulated system. To this end, we analyse the simulation results of these methods for molecular systems with increasingly stretched bonds.