Electronic correlations in organometallic complexes

TL;DR

This paper models organometallic complexes to understand their electronic properties, finding that simplified approximations are sufficient and electronic correlations are less critical, explaining the success of certain computational methods.

Contribution

It demonstrates that the CIS approximation effectively captures the low energy excitations of organometallic complexes, indicating electronic correlations are not crucial.

Findings

CIS approximation accurately reproduces low energy excitations

Electronic correlations are not essential for these complexes

Time-dependent DFT's success is explained by these findings

Abstract

We investigate an effective model for organometallic complexes (with potential uses in optoelectronic devices) via both exact diagonalisation and the configuration interaction singles (CIS) approximation. This model captures a number of important features of organometallic complexes, notably the sensitivity of the radiative decay rate to small chemical changes. We find that for large parameter ranges the CIS approximation accurately reproduces the low energy excitations and hence the photophysical properties of the exact solution. This suggests that electronic correlations do \emph{not} play an important role in these complexes. This explains why time-dependent density functional theory works surprisingly well in these complexes.