An assessment of frozen natural orbitals and band gaps using equation of motion coupled cluster theory: a case study on polyacene and trans-polyacetylene

TL;DR

This paper evaluates the use of frozen natural orbitals in equation of motion coupled cluster calculations to efficiently estimate band gaps in polyacene and trans-polyacetylene, demonstrating tunable accuracy with significantly reduced computational cost.

Contribution

It introduces a method to use FNOs for band gap calculations that balances accuracy and computational efficiency in complex organic materials.

Findings

FNOs can significantly reduce core-hours needed for calculations.

Errors in electron affinities and ionization potentials are tunable.

FNO truncation schemes relate systematically to basis set choices.

Abstract

Frozen natural orbitals (FNOs) are used to augment IP/EA-EOM-CCSD calculations targeting the band gap of trans-polyacetylene and polyacene. We show the resulting electron affinities (EAs), ionization potentials (IPs), and extrapolated band gaps incur errors that are largely tunable to a desired accuracy, yet require many orders of magnitude fewer core-hours as compared to the corresponding full calculation. The relationship between various FNO truncation schemes and (cc-pV$n$Z) basis set is also examined.