Insufficient description of dispersion in B3LYP and large basis set superposition errors in MP2 calculations can hide peptide conformers

B3LYP/6-31+G(d) and MP2/6-31+G(d) predict different structures for one Tyr–Gly conformer due to missing dispersion in B3LYP and large BSSE in MP2. B3LYP/6-31+G(d) and MP2/6-31+G(d) calculations predict markedly different structures for one Tyr–Gly conformer. Calculation of the energy profile for rot...

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Bibliographic Details
Published in:Chemical physics letters 2007-07, Vol.442 (1), p.42-46
Main Authors: Holroyd, Leo F., van Mourik, Tanja
Format: Article
Language:English
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Summary:B3LYP/6-31+G(d) and MP2/6-31+G(d) predict different structures for one Tyr–Gly conformer due to missing dispersion in B3LYP and large BSSE in MP2. B3LYP/6-31+G(d) and MP2/6-31+G(d) calculations predict markedly different structures for one Tyr–Gly conformer. Calculation of the energy profile for rotation around the glycine C α–N bond reveals one minimum in the B3LYP profile ( ϕ gly = 180°) and two in the MP2 profile (∼75° and 280°). Large intramolecular BSSE values are responsible for masking the 180°-minimum in the MP2 profile: approximate elimination of BSSE in the MP2 calculations – by (1) correction using BSSE values from complexes of phenol and N-formylglycine, (2) the application of local MP2, or (3) employing large basis sets (aug-cc-pVTZ/QZ) and density fitting – yields an unambiguous triple-well potential.
ISSN:0009-2614
1873-4448
DOI:10.1016/j.cplett.2007.05.072