Application to close-packed metal surfaces

In general, for an oblique lattice in two dimensions with primitive vectors ai and ao, the total conductance G can be expanded into a two-dimensional Fourier series. 

For a close-packed surface with hexagonal symmetry, up to the lowest nontrivial Fourier components, only the Fourier coefficients at k = 0 and the six equivalent points are significant. Because of the axial symmetry of the conductance function (r) on each site, the Fourier coefficients at these six points, [ G, o(z), C, o(z), Go.i(z), Go., (z), G,i(z), and G-i, i(z) ], are equal. We denote it as Gi(z). Up to this term. 

The theoretical expression of the topological STM image can be written in the form  

By comparing this with the results for surfaces with tetragonal symmetry, it is clear that the only difference is the factor of 8 in Eq. (6.29) is replaced by 9/2. With the same lattice constant, the corrugation amplitude of a surface with hexagonal symmetry is smaller than that for a surface with tetragonal symmetry by a factor of 9/16=0.5625. The decay constant of the corrugation is 

In the last column of Table 6-2, the ratios of the corrugation amplitudes with respect to the x-wave case are given for a surface with atomic distance a=2.88 A and work function j =3.5 eV. The relevant quantities are K = 0.96 A h = 2.52 , and y = 3.17 A. For most metals, the enhance- 

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