Electronically excited state geometries and vibrational frequencies calculated using the algebraic diagrammatic construction scheme for the polarization propagator

Abstract

• The aug-cc-pVTZ basis set shows convergence for the properties and methods tested. • Geometries using ADC methods are similar in accuracy to TDDFT. • Harmonic frequencies are well treated by ADC methods and improve with the order. • Scaling factors can be used to improve ADC harmonic frequencies. • Spin-Opposite-Scaling further improves the frequency match for the ADC(2). The algebraic diagrammatic construction (ADC) scheme for the polarization propagator provides a series of ab initio methods for the calculation of electronically excited states. Here we examine the accuracy of these methods for calculating excited state geometries and excited state harmonic vibrational frequencies for open-shell singlet excited states. A range of ADC methods have been assessed up to third-order, including both the strict and extended second-order schemes and spin-opposite scaling. Third-order ADC is found to provide a high level of agreement for both the experimental excited state geometry and frequency values, while second-order ADC is improved using spin-opposite scaling.