Post-CCSD(T) Thermochemistry of Chlorine Fluorides as a Challenging Test Case for Evaluating Density Functional Theory and Composite Ab Initio Methods

Karton, Amir; Haasler, Matthias; Kaupp, Martin

doi:10.1002/cphc.202400750

Author(s)

Karton, Amir

Haasler, Matthias

Kaupp, Martin

Publication Date

2025-02-01

Abstract

Quantum chemistry plays a key role in exploring the chemical properties of highly reactive chlorine polyfluoride compounds (ClFn). Here, we investigate the thermochemical properties of ClFn species (n=2–6) by means of high-level thermochemical procedures approximating the CCSDT(Q) and CCSDTQ5 energies at the complete basis set limit. We consider total atomization energies (TAEs), Cl F bond dissociation energies (BDEs), F2 elimination energies (F2 elim.), ionization potentials (IPs), and electron affinities (EAs). The TAEs have significant contributions from post-CCSD(T) correlation effects. The higher-order triple excitations, CCSDT CCSD(T), are negative and amount to 0.338 (ClF2), 0.727 (ClF3), 0.903 (ClF4), 1.335 (ClF5), and 1.946 (ClF6) kcal/mol. However, the contributions from quadruple (and, where available, also quintuple) excitations are much larger and positive and amount to +1.335 (ClF2), +1.387 (ClF3), +2.367 (ClF4), +2.399 (ClF5), and +3.432 (ClF6) kcal/mol. Thus, the contributions from post-CCSD(T) excitations exceed the threshold of chemical accuracy in nearly all cases. Due to their increasing hyper-valency and multireference character, the ClFn series provides an interesting and challenging test case for both density functional theory and low-level composite ab initio procedures. Here, we highlight the limitations in achieving overall chemical accuracy across all DFT and most composite ab initio procedures.

Citation

ChemPhysChem, 26(3), p. 1-11

ISSN

1439-7641

1439-4235

Link

https://hdl.handle.net/1959.11/63964

Language

en

Publisher

Wiley-VCH Verlag GmbH & Co KGaA

Title

Post-CCSD(T) Thermochemistry of Chlorine Fluorides as a Challenging Test Case for Evaluating Density Functional Theory and Composite Ab Initio Methods

Type of document

Journal Article

Entity Type

Publication

Author(s)	Karton, Amir Haasler, Matthias Kaupp, Martin
Publication Date	2025-02-01
Abstract	<p>Quantum chemistry plays a key role in exploring the chemical properties of highly reactive chlorine polyfluoride compounds (ClF<i><sub>n</sub></i>). Here, we investigate the thermochemical properties of ClF<i><sub>n</sub></i> species (<i>n</i>=2–6) by means of high-level thermochemical procedures approximating the CCSDT(Q) and CCSDTQ5 energies at the complete basis set limit. We consider total atomization energies (TAEs), Cl F bond dissociation energies (BDEs), F<sub>2</sub> elimination energies (F<sub>2</sub> elim.), ionization potentials (IPs), and electron affinities (EAs). The TAEs have significant contributions from post-CCSD(T) correlation effects. The higher-order triple excitations, CCSDT CCSD(T), are negative and amount to 0.338 (ClF<sub>2</sub>), 0.727 (ClF<sub>3</sub>), 0.903 (ClF<sub>4</sub>), 1.335 (ClF<sub>5</sub>), and 1.946 (ClF<sub>6</sub>) kcal/mol. However, the contributions from quadruple (and, where available, also quintuple) excitations are much larger and positive and amount to +1.335 (ClF<sub>2</sub>), +1.387 (ClF<sub>3</sub>), +2.367 (ClF<sub>4</sub>), +2.399 (ClF<sub>5</sub>), and +3.432 (ClF<sub>6</sub>) kcal/mol. Thus, the contributions from post-CCSD(T) excitations exceed the threshold of chemical accuracy in nearly all cases. Due to their increasing hyper-valency and multireference character, the ClF<i><sub>n</sub></i> series provides an interesting and challenging test case for both density functional theory and low-level composite ab initio procedures. Here, we highlight the limitations in achieving overall chemical accuracy across all DFT and most composite ab initio procedures.</p>
Citation	ChemPhysChem, 26(3), p. 1-11
ISSN	1439-7641 1439-4235
Link	https://hdl.handle.net/1959.11/63964
Language	en
Publisher	Wiley-VCH Verlag GmbH & Co KGaA
Title	Post-CCSD(T) Thermochemistry of Chlorine Fluorides as a Challenging Test Case for Evaluating Density Functional Theory and Composite Ab Initio Methods
Type of document	Journal Article
Entity Type	Publication

Post-CCSD(T) Thermochemistry of Chlorine Fluorides as a Challenging Test Case for Evaluating Density Functional Theory and Composite Ab Initio Methods

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