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Free keywords:
CCSD; STEOM; density; molecular properties; excited states
Abstract:
Similarity transformed equation of motion coupled cluster theory offers an efficient way of computing excited state energies by decoupling the space of singles from higher excitations. However, when computing properties with this method, one is left with a choice between an expensive method involving a transformation into the space of the singles and the doubles, or methods that approximate the full density. In this paper, we present a rigorous expectation value formulation of the density to compute transition properties and discuss its relation to other existing techniques. We confirm that the configuration interaction singles approximation we used in earlier studies oscillator strength values is a reliable one, but also that the current formulation provides a cost efficient improvement on it.
