title: Do H-bond features of silica surfaces affect the H2O and NH3 adsorption? Insights from periodic B3LYP calculations.
abstract: The adsorption of a single H(2)O and NH(3) molecule on different fully hydroxylated α-quartz, cristobalite, and tridymite surfaces has been studied at the B3LYP level of theory, within a periodic approach using basis sets of polarized triple-ζ 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 polymorph 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 (H(2)O and NH(3)) 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.
authors: Departament de Quimica, Universitat Autònoma de Barcelona, Bellaterra, Spain.
authors: Federico
authors: F
authors: Musso
authors: Piero
authors: P
authors: Ugliengo
authors: Mariona
authors: M
authors: Sodupe
mesh_terms: D000327:Adsorption; D000641:Ammonia / Q000737:chemistry*; D006860:Hydrogen Bonding; D011789:Quantum Theory; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D012822:Silicon Dioxide; D000641:Ammonia