Damped (linear) response theory within the resolution-of-identity coupled cluster singles and approximate doubles (RI-CC2) method

TL;DR

This paper presents an implementation of a complex solver for damped response functions within the RI-CC2 method, enabling efficient calculations of linear and nonlinear optical properties for large molecules.

Contribution

It introduces a partitioned formulation of the damped response theory within RI-CC2 that avoids storing double excitation amplitudes, facilitating applications to large molecular systems.

Findings

Accurate one-photon absorption cross sections for C60.

Electronic circular dichroism spectra for n-helicenes.

Calculated C6 dispersion coefficients for organic molecules and fullerenes.

Abstract

An implementation of a complex solver for the solution of the response equations required to compute the complex response functions of damped response theory is presented for the resolution-of-identity (RI) coupled-cluster singles and approximate doubles CC2 method. The implementation uses a partitioned formulation that avoids the storage of double excitation amplitudes to make it applicable to large molecules. The solver is the keystone element for the development of the damped coupled-cluster response formalism for linear and nonlinear effects in resonant frequency regions at the RI-CC2 level of theory. Illustrative results are reported for the one-photon absorption cross section of C60, the electronic circular dichroism of $n$-helicenes ($n$ = 5, 6, 7), and the $C_6$ dispersion coefficients of a set of selected organic molecules and fullerenes.