Poul Jo

Abstract: We have examined the response of an exact and an MCSCF reference state to a general time‐dependent field. The time development of both the exact and the MCSCF reference state have been parametrized in terms of explicit exponential time‐dependent transformations. The time development has been determined by requiring the Ehrenfest theorem to be satisfied through each order in the interaction between the molecular system and the field. The response of the exact and the MCSCF reference state has been used to evaluate linear, quadratic, and cubic response functions. It has been shown how a large variety of molecular properties may be expressed in terms of these response functions. It has also been demonstrated that molecular properties containing the electric dipole operator may be expressed in equivalent forms involving the momentum operator both for the exact and the MCSCF state. The MCSCF response functions have been transformed to computationally attractive expressions which do not contain summation indices over intermediate states and which allow direct techniques to be straightforwardly applied.

TL;DR: The linear and quadratic response functions have been determined for a coupled cluster reference state from the response functions, computationally tractable expressions have been derived for excitation energies, first and second-order matrix transition elements, transition matrix elements between excited states, and second and third-order frequency-dependent molecular properties as discussed by the authors.

TL;DR: In this article, a wave function based on Slater determinants expressed as products of alphastrings and betastrings is introduced, and a highly vectorized algorithm is developed for full CI and other RAS calculations.

TL;DR: In this paper, a polarization propagator approach was proposed to yield excitation energies, transition moments, and dynamic polarizabilities which are consistent through second order in the electronic repulsion.

TL;DR: In this article, the Hartree-Fock and correlation contributions to the interaction energy of the hydrogen-bonded complexes were computed in conventional calculations employing the aug-cc-pVXZ series of basis sets at the levels of second-order perturbation theory, and coupled-cluster theory with single and double excitations augmented by a perturbative triples correction.