Excitons and High Resolution Infrared Spectroscopy of Adlayers on Ionic Surfaces

Ewing, George E.

doi:10.1007/978-3-642-78632-7_6

Cited by 5 publications

(1 citation statement)

References 30 publications

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“…In contrast, the 1×1 monolayer structure was detected using He scattering on a NaCl crystal cleaved along 〈100〉 in vacuo . It is possible that infrared (IR) spectroscopy of water on the NaCl(100) surface may provide additional insight into the water−NaCl geometry as this method has been used to probe differences between monolayer and bilayer structures for ice interfaces. − In addition to the differences in the reported structures, there is also a spread in the reported water−NaCl binding energies ranging from 10 to 15 kcal/mol. , …”

Section: Introductionmentioning

confidence: 99%

Structure and Energetics of the Water/NaCl(100) Interface

1997

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A series of correlation-corrected periodic Hartree-Fock (PHF) calculations have been performed to evaluate the structure of a single layer of water adsorbed on NaCl(100). This work was motivated by differing experimental observations which assign the water/NaCl interface structure as either a monolayer, with a single adsorbate binding site, or a 4×2 bilayer model. Quantum mechanical binding energies were computed for several adsorbate/surface geometries corresponding to 1×1 and 2×1 monolayer structures and 4×2 bilayer structures. The calculations indicate that the binding energy per water molecule for the monolayer and bilayer models are very similar; the estimated PHF and correlation-corrected binding energies are 10 and 14 kcal/mol, respectively, for both models. When measured per unit surface area the 4×2 bilayer is energetically favored because it has a 50% greater packing density than the monolayer. The computed binding energies are consistent with experiment. These data show that the monolayer structure may be stable (or metastable) at low water coverages, but as the coverage is increased the bilayer structures become more favorable. The quantum mechanical data imply that the structure of the water/NaCl interface will be very sensitive to the sample preparation and experimental techniques used. The calculated binding energies for the 4×2 water bilayer geometries reveal the existence of many local minima on the potential energy surface which could result in the domaining of water on the NaCl(100) surface.

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Section: Introductionmentioning

confidence: 99%

Structure and Energetics of the Water/NaCl(100) Interface

1997

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Electrostatic model calculations on multiple adsorption at NaCl surfaces

Jug

Schmidt

Gerwens

1997

Int. J. Quant. Chem.

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ABSTRACT:A previously proposed electrostatic model for physisorption at ionic solids is extended to multiple adsorption of small molecules. A new algorithm is developed to avoid interpenetration of the interacting systems. The geometry optimization procedure is described. Ab initio calculations are used for the application of the method Ž . to the adsorption of CO and CO at NaCl 100 surfaces simulated by Na Cl clusters. The orientation of the adsorbate molecules in dependence on the cumulative atomic Ž . multipole moments CAMMs of the cluster atoms is discussed.

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Experimental and theoretical studies of the monolayer structure of OCS adsorbed on NaCl(001): Coexistence of orientationally inequivalent phases

Picaud

Giŗardet

Glebov³

et al. 1997

The Journal of Chemical Physics

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The structure of a physisorbed carbonyl sulfide (OCS) monolayer on a well-defined NaCl single crystal surface has been studied by helium atom scattering (HAS), low energy electron diffraction (LEED) and polarized Fourier-transform infrared spectroscopy, in the temperature range 30–100 K. The monolayer growth proceeds via large islands and both HAS and LEED indicate a (2×1) commensurate structure with two molecules per unit cell. The binding energy is estimated to be about 0.26 eV from desorption experiments. By contrast, the occurrence of three intense and three weaker absorption peaks in the infrared spectrum of the asymmetric stretching vibration ν3 is difficult to reconcile with the conclusions drawn from HAS and LEED. Therefore semi-empirical potential calculations are performed to determine the monolayer structure. Energy minimization rules out a high molecular density for the layer, and shows the existence of two isoenergetical (2×1) and (2×2) phases with respectively two and four molecules per unit cell, which differ only by the orientations of the molecules. Because of their similar geometry, these two structures cannot be discriminated by HAS and LEED, but the mixing of these two phases with different vibrational couplings between the admolecules provides a reasonable interpretation of the main features of the infrared spectrum.

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Excitons and High Resolution Infrared Spectroscopy of Adlayers on Ionic Surfaces

Cited by 5 publications

References 30 publications

Structure and Energetics of the Water/NaCl(100) Interface

Structure and Energetics of the Water/NaCl(100) Interface

Electrostatic model calculations on multiple adsorption at NaCl surfaces

Experimental and theoretical studies of the monolayer structure of OCS adsorbed on NaCl(001): Coexistence of orientationally inequivalent phases

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