Linear and nonlinear optical properties from TDOMP2 theory

TL;DR

This paper introduces the TDOMP2 and TDNOMP2 theories for real-time simulation of optical properties, demonstrating their accuracy in predicting spectra and polarizabilities compared to established methods.

Contribution

It derives the TDOMP2 and TDNOMP2 theories from the time-dependent bivariational principle and applies them to compute optical properties, showing improved accuracy over TDCC2.

Findings

TDOMP2 spectra match TDCC2 quality

Polarizabilities from TDOMP2 are closer to TDCCSD

Hyperpolarizabilities from TDOMP2 outperform TDCC2

Abstract

In this work we present a derivation of the real-time time-dependent orbital-optimized M{\o}ller-Plesser TDOMP2 and its biorthogonal companion, time-dependent non-orthogonal OMP2 (TDNOMP2), theory starting from the time-dependent bivariational principle and a parametrization based on the exponential orbital-rotation operator formulation commonly used in time-independent molecular electronic-structure theory. We apply the TDOMP2 method to extract absorption spectra and frequency-dependent polarizabilities and first hyperpolarizabilities from real-time simulations, comparing the results with those obtained from conventional time-dependent coupled-cluster singles and doubles (TDCCSD) simulations and from its second-order approximation TDCC2. We also compare with results from CCSD and CC2 linear and quadratic response theory. Our results indicate that while TDOMP2 absorption spectra are of the same quality as TDCC2 spectra, frequency-dependent polarizabilities and hyperpolarizabilties from TDOMP2 simulations are significantly closer to TDCCSD results than those from TDCC2 simulations.