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Article Dans Une Revue Physical Chemistry Chemical Physics Année : 2019

Isotope effect on hydrogen bond symmetrization in hydrogen and deuterium fluoride crystals by molecular dynamics simulation

Effet isotopique sur la symétrie de liaison hydrogène dans les cristaux d'hydrogène et de fluorure de deutérium par simulation de dynamique moléculaire

Résumé

The isotope effect on the collective proton/deuteron transfer in hydrogen and deuterium fluoride crystals has been investigated at 100 K by ab initio quantum-thermal-bath path-integral molecular dynamics (QTB-PIMD) simulation. The deuterons within a planar zigzag chain of the orthorhombic structure simultaneously flip between covalent and hydrogen bonds due to the barrier crossing through tunnelling. The height of the corresponding static barrier normalized for one deuteron is 29.2 meV. In the HF crystal, all the protons are located at the center of the heavy-atom distance. This evidences the symmetrization of the H-bonds, and indicates that the proton zero-point energy is above the barrier top. The decrease of the heavy-atom distance due to quantum fluctuations in both HF and DF crystals corresponds to a large decrease and an increase of the hydrogen and covalent bond lengths, respectively. Upon deuteration, the increase of the heavy-atom distance (Ubbelohde effect) is in agreement with experimental data.
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Dates et versions

hal-02118446 , version 1 (21-05-2019)

Identifiants

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Hichem Dammak, Fabien Brieuc, Grégory Geneste, Marc Torrent, Marc Hayoun. Isotope effect on hydrogen bond symmetrization in hydrogen and deuterium fluoride crystals by molecular dynamics simulation. Physical Chemistry Chemical Physics, 2019, 21 (6), pp.3211-3217. ⟨10.1039/c8cp06949b⟩. ⟨hal-02118446⟩
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