Infrared spectra and structure of acetylene on sodium chloride (100)

Dunn, Seth; Ewing, George E.

doi:10.1021/j100192a021

Cited by 45 publications

(46 citation statements)

References 13 publications

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“…The overall bandshape of the 90% C 2 D 2 is similar to that of pure C 2 H 2 except the bandwidth which is 1 cm -1 narrower; the bandwidths remain nearly constant at x ) 0.6-0.9 for C 2 D 2 . The small isotopic dependence (see Table 1) is similar to that found for monolayer C 2 H 2 on NaCl-(100) 12 but is in sharp contrast to the distinct effects observed in other surface systems, such as CO/NaCl(100) 21 and CO/Cu-(100). 26 In Figure 5, we also show the spectra of the CD stretch (ν 3 ) in C 2 HD at ν 0 ) 2544.9 cm -1 with Γ ) 3.0 cm -1 .…”

Section: Methodssupporting

confidence: 74%

Structure and Bonding of C₂H₂ on Diamond C(111)−1×1:H: Infrared Spectroscopy and Exciton Calculations

Chang

Lin

1996

J. Phys. Chem.

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The van der Waals interactions of acetylene with hydrogen-terminated diamond single crystal surfaces have been explored using infrared polarization spectroscopy at 83 K. By observing infrared spectra of the antisymmetric stretch of C 2 H 2 , the molecules are found to be adsorbed first on defect sites. This is followed by the adsorption on flat terraces that yields a single absorption at ν 0 ) 3225.6 cm -1 with a fwhm ) 5.4 cm -1 . The adsorbates lie nearly flat on the surface with a monolayer packing density of 5 × 10 14 molecules/ cm 2 and an adsorption energy of 23 kJ/mol. Isotope mixture experiments were also performed to provide information on the structure of the adsorbed phase. From the narrow width (fwhm < 3.0 cm -1 ) of the C 2 HD features and the result of exciton coupling calculations, it is suggested that the adsorbed layer forms a highly orientationally ordered superlattice. Two possible structures, (2×1) and (2×2) in ( 3× 3)R30°array, of the superlattice are proposed.

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Section: Methodssupporting

confidence: 74%

Structure and Bonding of C₂H₂ on Diamond C(111)−1×1:H: Infrared Spectroscopy and Exciton Calculations

Chang

Lin

1996

J. Phys. Chem.

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“…[31,[35][36][37] This system was chosen to test the new dispersion coefficients for ionic materials in a typical application. The unit cell for a full-coverage adsorption is shown in Figure 1.…”

Section: Adsorption Of Acetylene On Sodium Chloridementioning

confidence: 99%

“…Experimental values for the adsorption energy are À5.7 kcal mol À1 and À7.1 kcal mol À1 , [35,37] where the latter value corresponds to an experimental desorption enthalpy at half coverage. To the best of our knowledge, adsorption distances have not been measured experimentally, but previous theoretical investigations predict an equilibrium distance of about 3 .…”

Section: Adsorption Of Acetylene On Sodium Chloridementioning

confidence: 99%

“…After a brief outline of the theory in the next section and a discussion of the changes of dispersion in ionic systems, we will present as examples results for adsorption of acetylene on sodium chloride and carbon monoxide on magnesium oxide. These prototypical systems have been investigated previously by theoretical [27][28][29][30][31] and experimental [32][33][34][35][36][37] techniques.…”

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System‐Dependent Dispersion Coefficients for the DFT‐D3 Treatment of Adsorption Processes on Ionic Surfaces

et al. 2011

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Dispersion-corrected density functional theory calculations (DFT-D3) were performed for the adsorption of CO on MgO and C(2) H(2) on NaCl surfaces. An extension of our non-empirical scheme for the computation of atom-in-molecules dispersion coefficients is proposed. It is based on electrostatically embedded M(4)X(4) (M=Na, Mg) clusters that are used in TDDFT calculations of dynamic dipole polarizabilities. We find that the C(MM)(6) dispersion coefficients for bulk NaCl and MgO are reduced by factors of about 100 and 35 for Na and Mg, respectively, compared to the values of the free atoms. These are used in periodic DFT calculations with the revPBE semi-local density functional. As demonstrated by calculations of adsorption potential energy curves, the new C(6) coefficients lead to much more accurate energies (E(ads)) and molecule-surface distances than with previous DFT-D schemes. For NaCl/C(2) H(2) we obtained at the revPBE-D3(BJ) level a value of E(ads) =-7.4 kcal mol(-1) in good agreement with experimental data (-5.7 to -7.1 kcal mol(-1)). Dispersion-uncorrected DFT yields an unbound surface state. For the MgO/CO system, the computed revPBE-D3(BJ) value of E(ads) =-4.1 kcal mol(-1) is also in reasonable agreement with experimental results (-3.0 kcal mol(-1)) when thermal corrections are taken into account. Our new dispersion correction also improves computed lattice constants of the bulk systems significantly compared to plain DFT or previous DFT-D results. The extended DFT-D3 scheme also provides accurate non-covalent interactions for ionic systems without empirical adjustments and is suggested as a general tool in surface science.

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“…The value 2.5 Å of the molecule-substrate distance that we have found for acetylene/MgO(100) is somewhat smaller than the distance 2.81 Å between (100) planes of the low temperature phase of bulk acetylene, where the molecule arrangement is close to that in the acetylene monolayer on MgO [17]. Acetylene adsorbed onto another ionic substrate NaCl(100) has been studied by polarized infrared (IR) spectroscopy [18]. The IR spectra could be qualitatively explained by a bilayer structure, where molecules in each layer are tilted by about 10 ± from the surface plane direction.…”

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confidence: 72%

Structure of Physisorbed Molecules on an Oxide Surface from Potential Calculations and Dynamical Low-Energy Electron Diffraction Analysis: Acetylene on MgO(100)

et al. 1997

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Semiempirical potential calculations have been combined with a dynamical low-energy electron diffraction analysis to determine the complete structure of molecules physisorbed on an oxide surface, namely, acetylene (C 2 H 2 ) adsorbed on MgO(100) at T 88 K. This allows determination of the adsorption sites and the molecule-molecule and molecule-substrate distances. The results are consistent with molecules that lie almost parallel to the surface in a herringbone structure. Neither molecule nor substrate exhibits significant distortions, due to the weak physisorption. [S0031-9007 (97)03254-7] PACS numbers: 68.55.Jk, 34.20.Gj, 61.14.Hg Molecular adsorption, including physisorption, on oxides is of special importance for catalysis, since oxides play major roles both as active catalysts and as supports for metallic catalyst particles [1]: Zeolites, in particular, have attracted much attention [2]. While strong metal-support interactions remain under extensive study [3], there is a need for studying surfaces that are accessible to a wider range of surface science techniques, primarily external single-crystal surfaces [4]. MgO provides a most favorable model oxide crystal for this purpose: It is itself used as a support in catalysis. It is furthermore used as support for the growth of high-T c superconductors. MgO provides high-quality single-crystal surfaces while it is also available as uniform powder on whose large surface area molecular adsorption can be studied with neutron diffraction. Calculations [5], as well as low-energy electron diffraction (LEED) dynamical analyses [6,7] and medium-energy ion scattering analysis [8], have shown that the bare MgO(100) surface is only slightly perturbed from its bulk structure. Molecular adsorbates bearing strong dipole or quadrupole moments have been investigated on this surface. They are good probes of the surface electric field and have been used to evaluate the effective ionic charge q ‫ء‬ q͞e of the surface ions [9]. This effective charge is about 61.2, in agreement with theoretical models [10]. Acetylene has a strong quadrupole moment which is expected to interact strongly with the surface electric field gradient and give a molecular arrangement with strong quadrupole-quadrupole interactions. LEED adsorption isotherms on MgO(100) surfaces [11] as well as volumetric isotherms on powders [12] have provided adsorbate-substrate and adsorbateadsorbate interaction energies which have been compared to semiempirical potential calculations [11]. However, the detailed equilibrium structure given by the theoretical model must still be confronted with experimental results. The dynamical analysis of LEED intensities provides a unique way to obtain the complete structure: molecular adsorption sites, molecule-substrate distance, and orientation, in addition to any relaxation within the molecules and the substrate. However, this analysis require an approximate knowledge of the monolayer structure to start with, since it is a perturbationlike method. This is the reason why our approach c...

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Infrared spectra and structure of acetylene on sodium chloride (100)

Cited by 45 publications

References 13 publications

Structure and Bonding of C₂H₂ on Diamond C(111)−1×1:H: Infrared Spectroscopy and Exciton Calculations

Structure and Bonding of C₂H₂ on Diamond C(111)−1×1:H: Infrared Spectroscopy and Exciton Calculations

System‐Dependent Dispersion Coefficients for the DFT‐D3 Treatment of Adsorption Processes on Ionic Surfaces

Structure of Physisorbed Molecules on an Oxide Surface from Potential Calculations and Dynamical Low-Energy Electron Diffraction Analysis: Acetylene on MgO(100)

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Infrared spectra and structure of acetylene on sodium chloride (100)

Cited by 45 publications

References 13 publications

Structure and Bonding of C2H2 on Diamond C(111)−1×1:H: Infrared Spectroscopy and Exciton Calculations

Structure and Bonding of C2H2 on Diamond C(111)−1×1:H: Infrared Spectroscopy and Exciton Calculations

System‐Dependent Dispersion Coefficients for the DFT‐D3 Treatment of Adsorption Processes on Ionic Surfaces

Structure of Physisorbed Molecules on an Oxide Surface from Potential Calculations and Dynamical Low-Energy Electron Diffraction Analysis: Acetylene on MgO(100)

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Structure and Bonding of C₂H₂ on Diamond C(111)−1×1:H: Infrared Spectroscopy and Exciton Calculations

Structure and Bonding of C₂H₂ on Diamond C(111)−1×1:H: Infrared Spectroscopy and Exciton Calculations