Comment on: “Quantum Confinement in Hydrogen Bond” by Carlos da Silva dos Santos, Elso Drigo Filho, and Regina Maria Ricotta, Int. J. Quantum Chem. 2015, 115, 765-770.

Abstract

In Ref.[1], the characteristic vibrational shift of OH and NH stretching fundamental modes engaged in hydrogen bonds is attributed to a quantum confinement effect. The latter is modeled by introducing infinite potential energy boundaries for the hydrogen motion at short and long hydride bond distances into a single-well one-dimensional (1D) Morse oscillator. Such a confinement will necessarily lead to an increase of the gap between the ground state (quantum number v 5 0) and the first vibrationally excited state (quantum number v 5 1), if it occurs in a region of significant wavefunction amplitude. This remains valid if the onset of the confinement is somewhat smooth rather than instantaneous, although the latter case is easier to analyze. Instead of a formal variational proof, one may argue within the framework of diffusion Monte Carlo.[2]

Reply to the Comment on: “Quantum Confinement in Hydrogen Bond” by Carlos da Silva dos Santos, Elso Drigo Filho, and Regina Maria Ricotta, Int. J. Quantum Chem. 2015, 115, 765-770

“…There are no arguments or strong evidence at the moment to abandon this attitude in the incorporation of confinement to the description of hydrogen bonds in different media. Thus, it is understood that the use of experimental results for gases, as suggested by Heger and Suhm, [3] can be used for further tests to the results presented but do not invalidate the results obtained in. [1] We stress that the main objective of our work is to support the hypothesis that the confinement should be an important component for the description of hydrogen bonds and that the results, when the confinement is incorporated, describe the experimental data studied without exceeding the errors declared.Despite the arguments raised, it is not clear that the quantum confinement hypothesis in the description of hydrogen bonds should be ruled out.…”