Abstract

RAMIREZ, José-Zeferino; VARGAS, Rubicelia  and  GARZA, Jorge. The Role of the Linearity on the Hydrogen Bond in the Formamide Dimer: a BLYP, B3LYP, and MP2 Study. J. Mex. Chem. Soc [online]. 2008, vol.52, n.1, pp.31-35. ISSN 1870-249X.

Quantum chemistry methods have been proven to be a very useful tool to study chemical systems stabilized by hydrogen bonds. The two theoretical methodologies most frequently used are the Density Functional Theory (DFT), in its Kohn-Sham version, and the second order Maller-Plesset Perturbation Theory (MP2). Lately, many studies have been focused on weak hydrogen bonds (binding energies < 4 kcal/mol) because such contacts might have a relevant role in the molecular ensemble. However, there are some results about this type of interactions where the Kohn-Sham model and MP2 give different answers. By testing two exchange-correlation functionals, BLYP and B3LYP, we are proposing in this paper that such a discrepancy will happen mainly when the hydrogen bond is far from the linearity; we present this hypothesis on the formamide dimer as an example. We found that, even when this dimer exhibits two hydrogen bonds (N-H... O) with moderate strength, the MP2 and the two exchange-correlation functionals, considered in this work, predict different potential energy surfaces when the geometrical parameters of the hydrogen bond are distorted and a limited basis set is used.

Keywords : Hydrogen bond; DFT; MP2; Theoretical approach; Basis set functions; Formamide dimer.

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