Trends in lateral interactions between CO chemisorbed on low index copper surfaces

Adsorbate-induced substrate relaxation and the adsorbate–adsorbate interaction

“…[7] seem more probable, although the origin of the attractive W 2 (if it is real) is not clear. For the on-top CO on Cu(111), the same authors found W 2 = 107 K, W 3 > 800 K, W 4 = 155 K [6]. The value of W 3 seems too large compared with the other two, but otherwise the results are quite similar to CO/Pt(111).…”

“…In the latter case, even a weak attraction is possible owing to partly collinear displacements induced by the two adsorbates on more distant surface atoms. the values W 2 = 0 and W 3 = 400 K were found for Rh(100) [7], while the values suggested for Cu(100) were W 2 = −33 K and W 3 = 13 K [6]. It is interesting that the continuum elastic theory [2] also gives a strong repulsion in the 110 direction and possibly a weak attraction in the 100 direction between adsorbates on (100) surfaces of noble metals.…”

“…For adsorbates separated by a few atomic spacings, however, the continuum theory may not be valid. More recently, in a series of papers Kevan et al [3][4][5][6][7] have determined adsorbate-adsorbate interaction energies for CO at several metal surfaces, using a transfer-matrix analysis of thermal desorption spectra. They have also qualitatively discussed the adsorbate-induced strain as a possible mechanism of the adsorbate-adsorbate interaction at intermediate range, i.e., several substrate atoms apart.…”

“…Interaction energies have also been determined for CO chemisorbed on Rh [7,25] and Cu [6] surfaces. We discuss these systems only qualitatively, since the proposed values are still uncertain, and there is no quantitative data on other adsorbate-induced properties.…”

RDS investigation of adsorption and surface ordering processes on Cu(110)

“…The repulsive interaction along [110] keeps the CO chains away from each other as observed by STM [18] and He scattering [17]. At large distances between the chains (such as in the (3 Â 1) phase) the interaction will be small or might even become slightly attractive by 7-10 meV [19]. The (3 Â 1) phase can thus be considered as the limiting case, where the distance between neighboring CO rows in the [110] direction is larger than or equal to three times the Cu distance and the interaction between the rows is attractive, whereas the interaction switches into repulsive when the distance becomes shorter than in the (3 Â 1) phase.…”