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Figure 6
(a) This is the full calculated 2θ profile from N = 100 crystal planes (parallel to the surface plane) a distance d = 0.5654 nm apart and scattering strength of unity, i.e. there is one length scale (Cu Kα1). The conventional diffraction peak indices are given as 100, 200, …, 700 and in the new theory these peaks are harmonics associated with the path lengths λ, 2λ, …, 7λ between adjacent planes. The intensity peak values correspond to N2 and have not been modified by any factors. The truncation points used to define the range for individual structure factors occur in the dips between the peaks. (b) Inserting three more planes with the same periodicity but displaced by a fraction of this period at 0.25d, 0.5d and 0.75d and having scattering strengths of 0.9, 1.0 and 0.9, respectively, changes the profile dramatically. Individually each of these planes would reproduce the same profile as in (a), with the maxima modified by the scattering strength. However, when their amplitudes are combined, the peaks associated with path lengths of integer wavelengths n = 1, 3, 5, 7 result in their amplitudes cancelling – with n = 2, 6 the intensities are suppressed and the intensity for n = 4 is increased to (4N)2. This example profile is characteristic of a zincblende structure along the 〈100〉 direction.

ISSN: 2053-2733
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