Intramolecular BSSE and dispersion affect the structure of a dipeptide conformer
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B3LYP and MP2 calculations with the commonly-used 6-31+G(d) basis set predict qualitatively different structures for the Tyr-Gly conformer book1, which is the most stable conformer identified in a previous study (Mol. Phys. 104, 559-570, 2006). The structures differ mainly in the ψTyr Ramachandran angle (138° in the B3LYP structure and 120° in the MP2 structure). The causes for the discrepant structures are attributed to missing dispersion in the B3LYP calculations and large intramolecular BSSE in the MP2 calculations. The correct ψTyr value is estimated to be 130°. The MP2/6-31+G(d) profile identified an additional conformer, not present on the B3LYP surface, with a ψTyr value of 96° and a more folded structure. This minimum is however likely an artefact of large intramolecular BSSE values. We recommend the use of basis sets of at least quadruple-zeta quality in DFT, DFT-D and MP2 calculations in cases where intramolecular BSSE is expected to be large.
Hameed , R , Khan , A & Van Mourik , T 2018 , ' Intramolecular BSSE and dispersion affect the structure of a dipeptide conformer ' , Molecular Physics , vol. 116 , no. 9 , pp. 1236-1244 . https://doi.org/10.1080/00268976.2017.1418029
© 2017 Informa UK Limited, trading as Taylor & Francis Group. This work has been made available online in accordance with the publisher’s policies. This is the author created accepted version manuscript following peer review and as such may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1080/00268976.2017.1418029
DescriptionRH acknowledges funding from Higher Education Commission of Pakistan for her visit to the University of St Andrews as a visiting scholar.
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