Hydrogen bond cooperativity and electron delocalization in hydrogen fluoride clusters

Abstract

We investigate the energetic, structural, electronic and thermodynamics properties of hydrogen fluoride cluster, (HF)n, in the range n=2–8, by ab initio methods and density functional theory (DFT). The ab initio methods chosen were Hartree–Fock (RHF) and second-order Mo/ller–Plesset perturbation theory (MP2). The DFT calculations were based on Becke’s hybrid functional and the Lee–Yang–Parr correlation functional (B3LYP). We found that symmetric cyclic clusters are the most stable structure, and that large cooperative effects, particularly from trimer to tetramer are present, in binding energy, and hydrogen bond distance. An analysis of the topology of the electron density reveals a linear correlation between the binding energy per hydrogen bond and the density at the hydrogen bond critical point and the Cioslowski covalent bond order. Based on these correlations, hydrogen bond cooperativity is associated with the electronic delocalization between monomers units. Analysis of the thermodynamics properties shows that the enthalpy changes are determined by the electronic cooperative effects, while the entropic statistical factors are fundamental in the relative stability of these clusters. Finally, for the trimer and tetramer, nonstable linear zigzag chains where found in a detailed analysis of the potential energy surfaces.

Secondary Interaction Contribution in Hydrogen-Bonded Complex: Theoretical Model Study in Hydrogen Fluoride Trimer

“…The stabilization energy per one hydrogen bond in the cluster significantly arises from the tetramer, but it is not remarkably changed between the dimer and the trimer [13]. Our results were in good agreement with the results of Rincón et al [13]; thus, we can safely deal with these trimer systems as the model of hydrogen bond sites without consideration of three-body interaction. Taking account of these results, MP2and QCISD(T) studies were carried out based on the hydrogen fluoride dimer systems.…”

Counterpoise-corrected geometries and harmonic frequencies of N-body clusters: Application to (HF)n (n=3,4)

“…, 32 the open chain structures for the HF trimer and tetramer are first-order saddle points connecting two equivalent cyclic configurations. Our results are consistent with their findings in all the cases.…”

Many‐body energy decomposition analysis of cooperativity in hydrogen fluoride clusters

“…Since the equations of classical electrostatic include only pairwise additive interactions of localized monomers, the existence of these effects can be considered a departure from the classical electrostatic model of hydrogen bonding, indicating the inadequacy of considering its electrostatic picture alone, and, perhaps even more important, suggesting the presence of significant electronic delocalization. Employing ab initio and density functional theory (DFT) methods, our group [9] has found evidence of this kind of effect. Large cooperative effects for the binding energy per HB in hydrogen fluoride clusters were found, as reflected in the geometric parameters of the clusters and the topological properties of the electron charge density.…”