Electronic transition dipole moment: A semi‐biorthogonal approach within valence universal coupled cluster framework

Abstract

Electronic dipole strengths (square of transition moments) and oscillator strengths are evaluated for various transitions, arising from the ground state to a few valence excited states. Parallel to two other methods of calculating the dipole strength within the Fock‐space multireference coupled cluster framework, a new semi‐biorthogonal approach is formulated and implemented in this article. This semi‐biorthogonal approach can evaluate dipole strengths at a lower computational effort than the biorthogonal approach without compromising on the accuracy. This new method is compared and tested against the previously developed expectation value and biorthogonal approach for various molecular transitions. © 2014 Wiley Periodicals, Inc.

Finite-Field Calculations of Transition Properties by the Fock Space Relativistic Coupled Cluster Method: Transitions between Different Fock Space Sectors

“…Due to the exponential form of the wave operators, the expressions for property matrix elements between the FS CC wavefunctions in terms of cluster amplitudes and model eigenvectors have the form of (quasi-) nonterminating series. Truncating these series, one arrives at computational schemes which had been successfully applied to ab initio calculations of transition probabilities in small systems (see, e.g., [11][12][13] and references therein). The simplest scheme of this kind includes abandoning of all the amplitude-dependent terms, and estimating the required property matrix elements between the FS (R)CC wavefunctions by the transition amplitudes between the corresponding model space functions (e.g., left and right eigenvectors of the effective Hamiltonian) [14,15].…”

Finite-Field Calculations of Transition Properties by the Fock Space Relativistic Coupled Cluster Method: Transitions between Different Fock Space Sectors

“…Truncating these series, one arrives at computational schemes which had been successfully applied to ab initio calculations of transition probabilities in small systems (see e.g. [11][12][13] and references therein). The simplest scheme of this kind includes abandoning of all the amplitude-dependent terms, and estimating the required property matrix elements between the FS (R)CC wavefunctions by the transition amplitudes between the corresponding model space functions (e.g.…”

A simple scheme for calculating approximate transition moments within the equation of motion expectation value formalism

“…13 A very efficient implementation of transition dipole moments within the framework of CC2 theory has been reported by Hättig and Köhn using the densityfitting/resolution of the identity approach 14 and Baudin et al 15 as well as Schütz and co-workers 16 using the local correlation approach. The implementation of transition dipole moments for other variants of coupled cluster or related methods, such as similarity transformed EOMCC (STEOMCC), 17 Fock space multireference coupled cluster (FSMRCC), 18,19 and symmetry adapted cluster/configuration interaction (SAC-CI), 20 has also been reported.…”