dc.contributor.author |
Cukrowski, Ignacy
|
|
dc.contributor.author |
Polestshuk, Pavel M.
|
|
dc.date.accessioned |
2018-01-15T08:38:23Z |
|
dc.date.issued |
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 |
http://www.rsc.org/journals-books-databases/about-journals/PCCP |
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) |
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dc.identifier.other |
10.1039/c7cp02216f |
|
dc.identifier.uri |
http://hdl.handle.net/2263/63538 |
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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 |