Applications of a perturbation-aware local correlation method to coupled cluster linear response properties

TL;DR

This paper evaluates the accuracy and efficiency of PNO++, combined PNO++, and PNO methods for coupled cluster response properties across various molecular systems, highlighting their relative strengths and limitations.

Contribution

The study extends and tests PNO++ and combined PNO++ methods on larger molecules, comparing their performance to PNO in response property calculations.

Findings

PNO++ and combined PNO++ reduce localization errors in linear response properties.

PNO performs better for correlation energies, but combined PNO++ offers similar accuracy.

All methods show comparable errors for complex 3D molecules, with slight variations depending on the system.

Abstract

We have investigated the efficacy of two recently proposed variations of the pair-natural-orbital approach to reducing the scaling of coupled cluster property calculations. In particular, we have extended our implementations of the PNO++ and combined PNO++ methods, which make use of field-aware pair-densities to define the virtual-orbital spaces used to describe electron correlation effects, in order to test their accuracy, efficiency, and robustness on larger molecular systems than previously investigated. For fluoroalkane chains up to 1-fluoroheptane we find that the PNO++ and combined PNO++ methods yield smaller localization errors in response properties than PNO for similarly compact virtual spaces, and, while the PNO method performs better than the PNO++ method for correlation energies, the combined PNO++ method recovers similar accuracy for correlation energies to the PNO method. For more three-dimensional molecular structures such as $\alpha$- and $\beta-$pinenes, the PNO, PNO++, and combined PNO++ methods all yield similar errors for response properties, whereas for ($S$)-1-phenylethanol, the PNO method performs slightly better than the other two approaches. We also investigate the use of a product density to define the virtual space, as well as two candidates for defining weak-pair contributions.