Do H-Bond Features of Silica Surfaces Affect the H2O and NH3 Adsorption? Insights from Periodic B3LYP Calculations

作者：Musso Federico; Ugliengo Piero^*; Sodupe Mariona

来源：Journal of Physical Chemistry A, 2011, 115(41): 11221-11228.

DOI：10.1021/jp203988j

The adsorption of a single H2O and NH3 molecule on different fully hydroxylated alpha-quartz, cristobalite, and tridymite surfaces has been studied at the B3LYP level of theory, within a periodic approach using basis sets of polarized triple-zeta quality and accounting for basis set superposition error (BSSE). Fully hydroxylated crystalline silica exhibits SiOH as terminal groups whose distribution and H-bond features depend on both the considered silica polyrnorph and the crystallographic plane, which gives rise to isolated, H-bond interacting SiOH pairs or infinitely connected H-bond chains. A key point of the present study is to understand how the H-bond features of a dry crystalline silica surface influence its adsorption properties. Results reveal that the silica-adsorbate (H2O and NH3) interaction energy anticorrelates with the density of SiOH groups at the surface. This counterintuitive observation arises from the fact that pre-existing H-bonds of the dry surface need to be broken to establish new H-bonds between the surface and the adsorbate, which manifests in a sizable energy cost due to surface deformation. A simple method is also proposed to estimate the strength of the pre-existing H-bonds at the dry surfaces, which is shown to anticorrelate with the adsorbate interaction energy, in agreement with the above trends.

• 出版日期2011-10-20