Choosing Bad versus Worse: Predictions of Two-Photon-Absorption Strengths Based on Popular Density Functional Approximations.

Marta Chołuj,Sebastian P Sitkiewicz,Robert Zaleśny,Kenneth Ruud,Maarten T P Beerepoot,Eduard Matito,Md Mehboob Alam

doi:10.1021/acs.jctc.1c01056

Abstract

We present a benchmark study of density functional approximation (DFA) performances in predicting the two-photon-absorption strengths in π-conjugated molecules containing electron-donating/-accepting moieties. A set of 48 organic molecules is chosen for this purpose, for which the two-photon-absorption (2PA) parameters are evaluated using different DFAs, including BLYP, PBE, B3LYP, PBE0, CAM-B3LYP, LC-BLYP, and optimally tuned LC-BLYP. Minnesota functionals and ωB97X-D are also used, applying the two-state approximation, for a subset of molecules. The efficient resolution-of-identity implementation of the coupled-cluster CC2 model (RI-CC2) is used as a reference for the assessment of the DFAs. Two-state models within the framework of both DFAs and RI-CC2 are used to gain a deeper insight into the performance of different DFAs. Our results give a clear picture of the performance of the density functionals in describing the two-photon activity in dipolar π-conjugated systems. The results show that global hybrids are best suited to reproduce the absolute values of 2PA strengths of donor–acceptor molecules. The range-separated functionals CAM-B3LYP and optimally tuned LC-BLYP, however, show the highest linear correlations with the reference RI-CC2 results. Hence, we recommend the latter DFAs for structure–property studies across large series of dipolar compounds.

Highlights

Light−matter interactions have been the subject of intensive research both experimentally and theoretically for decades
We will start with an analysis of the two-photon-absorption strengths computed with response theory using both the reference resolution-ofidentity implementation of the coupled-cluster CC2 model (RI-CC2) method and different density functional approximation (DFA) (BLYP, B3LYP, PBE, PBE0, (OT)-LC-BLYP, and CAM-B3LYP) for the whole set of 48 molecules
We discuss in greater detail the results obtained using OTLC-BLYP, before we end by a comparison with some more heavily parametrized DFAs

Summary

Introduction

Light−matter interactions have been the subject of intensive research both experimentally and theoretically for decades. Theoretical chemistry plays an important role in this area of research.[21,22,29−39] Advanced electronic-structure calculations allow the optical properties of molecules and materials to be predicted accurately,[40] and allow the elucidation of results of experimental measurements. This holds in particular for the analysis of spectroscopic signatures in nonlinear absorption spectra. Simulations of 2PA spectra can be challenging for computational chemistry, especially when

Objectives

Results

Conclusion