Reconstruction missing row

Pt(l 10) is known experimentally to reconstruct into the so-called missing-row reconstruction. In this reconstruction, alternate rows from the top layer of the surface in a (2 x 1) surface unit cell are missing. Use a supercell defined by a (2 x 1) surface unit cell of Pt(110) to compute the surface energy of the unreconstructed and reconstructed surfaces. Why does this comparison need to be made based on surface energy rather than simply based on the total energy of the supercells Are your results consistent with the experimental observations Use similar calculations to predict whether a similar reconstruction would be expected to exist for Cu(110). 

The (2x1) structure is also known as missing-row reconstruction because one out of two rows of atoms, aligned along the [110] direction, is missing from the surface layer. We stress also that there are two different realizations of these reconstructed states, in which either the even or the odd rows are missing. 

Fig. 1 shows a top and a side view of the missing-row reconstructed structure. Along the [001] direction the surface assumes a hill-and-valley profile, where the sides of the hills are actually (111) microfacets. In the (111) orientation, surface atoms are closely packed, therefore such orientations are energetically favored. 

The predicted shapes could be observed in experiments on equilibrium shapes of crystals with (110) missing-row reconstructed facets. 

Submonolayer of Ni deposited in the temperature range of 130-180 K on the missing-row reconstructed Au(llO)-(1 X 2) surface has been analyzed using STM [465]. An order within the thin epitaxial AuNi film deposited on an Au(lOO) surface, accompanying temperature changes, has been investigated by applying X-ray diffraction [466]. 

The (110) surfaces of Au [24], Pt [25] and Ir [26] display (2 x 1) LEED patterns, which are described by missing row reconstructions, in which every other closed-packed atomic row along [110] is missing. The driving force in this case seems to be the formation of (111) microfacets with their lower surface energy [22]. The resulting ID channels have been used as a template for assembling molecular wires , e.g. of the amino acid cysteine [27]. 

Figure 3 Geometry of missing row reconstructed Ag(l 0 0), of Ag(41 0) and of Ag(2 1 0). For the Ag( 1 0) surfaces the scattering plane of both incoming molecules and electrons is aligned along the (I, n, 0) direction (across the monoatomic steps). The surface unit cell and the angles corresponding to normal incidence on the (11 0) and (1 0 0) nanofacets are also drawn.

Figure 2.4 Missing row reconstruction of the fcc(llO) surface to make larger areas of (111) structure the resulting form is designated (110) (2x1).

Au (110) (fee) (2x1) Missing-row reconstruction studied by channeling and blocking, top layer spacing contracted by 18%, second layer spacing expanded by 4% from bulk value of 1.44 A. Third layer buckled by 0.10 A or 7%, with atoms under missing row moving up, alternate rows down. MEIS/3/... 

Sulfur is adsorbed in 3-fold sites on the (111) facets left by the clean-surface missing-row reconstruction. The first Ir-Ir spacing is contracted by 3.3%, the second expanded by 1.3%. Ir-S is 2.39 A for first-layer Ir atoms and 2.26 A for second-layer Ir atoms. 

The LEED pattern of the clean (1x2) reconstructed Au(llO) is presented in Fig. 16 [72] together with a schematic representation of the missing row reconstructed surface. The peculiar geometry of the missing row reconstructed surfaces of fee metals offers a priori a unique way to generate linear structures of adatoms and to measure their specific properties. However, as will be seen below, in the present case, the situation is more complex. 

Fig. 16. LEED diagram observed for the (1x2) reconstructed Au(llO) surface (130 eV electron energy) and schematic representation of the corresponding missing row reconstruction.

Haase O, Koch R, Borbonus M, Rieder KH (1991) Role of regular steps on the formation of missing-row reconstructions - oxygen-chemisorption on Ni(771). Phys Rev Lett 66 1725... 

The locations of the O atoms deduced from XPD are consistent with previous studies on this system using EEIS, STM, and surface-enhanced x-ray absorption hne-structure spectroscopy (SEXAES). Similar (2 x l)-0 phases on Cu(llO) and Ni(llO) also have missing-row reconstructions. 

Fig. 9.7. Schematic of some of the key rearrangement mechanisms at surfaces (adapted from Liith (1993)) (a) surface relaxation, (h) surface reconstruction and (c) missing-row reconstruction.

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