Reliability of interacting quantum atoms (IQA) data computed from post-HF densities : impact of the approximation used

Show simple item record Cukrowski, Ignacy Polestshuk, Pavel M. 2018-01-15T08:38:23Z 2017-05
dc.description.abstract The performance of BBC1, BBC2 and Müller approximations, in terms of reliability of IQA data, was investigated at the CCSD, CCSD(T) and MP2 levels using glycol, as a case study, in interpreting the relative stability of its conformers, one with H-bond type intramolecular interaction and the other with a steric clash between two O-atoms. The CCSD/BBC1 level appeared to be perfectly suited as a reference needed to evaluate all possible levels of theory/approximation combinations (LoT/LoA). We found the reliability trend LoT/BBC1 > LoT/BBC2 > LoT/Müller (as well as its origin) and concluded that the Müller approximation should not be used when the accuracy of IQA-defined energy terms is considered. Moreover, we have established that the requirement of reproducing, by IQA calculations, electronic energy is desirable but not a necessary requirement when a comparative approach is used, such as in FAMSEC-based analysis (FAMSEC = fragment attributed molecular system energy change). A new criterion is proposed to assess the quality of IQA data for comparative analyses, ΔE(IQA) ≈ ΔE, where ΔE(IQA) and ΔE are the IQA and electronic energy differences, respectively, between the fin-state and ref-state of a molecular system. The closer ΔE(IQA) approaches ΔE, the closer the FAMSEC data approach values obtained at the exceptionally well performing CCSD/BBC1 level, regardless of the LoT/LoA combination used. Importantly, the MP2/BBC1 level performed nearly as well as the CCSD/BBC1 level in comparative studies. The origin of the MP2/BBC1 approximation's exceptional and the MP2/Müller approximations's acceptable performance in explaining the relative stability of glycol conformers has been uncovered and discussed in detail. en_ZA
dc.description.department Chemistry en_ZA
dc.description.embargo 2018-05-30
dc.description.librarian hj2018 en_ZA
dc.description.sponsorship Tthe National Research Foundation of South Africa (Grant Number 105855). en_ZA
dc.description.uri en_ZA
dc.identifier.citation Cukrowski, I. & Polestshuk, P.M. 2017, 'Reliability of interacting quantum atoms (IQA) data computed from post-HF densities: impact of the approximation used', Physical Chemistry Chemical Physics, vol. 19, no. 25, pp. 16375-16386. en_ZA
dc.identifier.issn 1463-9076 (print)
dc.identifier.issn 1463-9084 (online)
dc.identifier.other 10.1039/c7cp02216f
dc.language.iso en en_ZA
dc.publisher Royal Society of Chemistry en_ZA
dc.rights © the Owner Societies 2017 en_ZA
dc.subject Interacting quantum atoms (IQA) en_ZA
dc.subject Fragment attributed molecular system energy change (FAMSEC) en_ZA
dc.subject BBC1 approximation en_ZA
dc.subject BBC2 approximation en_ZA
dc.subject Müller approximation en_ZA
dc.subject Two-electron density matrix (2EDM) en_ZA
dc.subject Systems en_ZA
dc.subject Molecules en_ZA
dc.subject Stability en_ZA
dc.subject Matrix en_ZA
dc.subject Occupied orbitals en_ZA
dc.title Reliability of interacting quantum atoms (IQA) data computed from post-HF densities : impact of the approximation used en_ZA
dc.type Postprint Article en_ZA

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