Diffuse and weak Bragg scattering from quasicrystals: Pitfalls and opportunities

Abstract

The influence of limited experimental reciprocal space resolution on the appearance of diffraction patterns from quasicrystals is discussed. Using simulated data from a perfectly ordered one-dimensional Fibonacci chain it is shown that realistic experimental resolution effects may lead to artificial 'diffuse scattering' of significant intensity. Two different diffuse features are identified in simulations of macroscopically sized crystals. A broad and almost smooth diffuse background is found, which strongly inceases with decreasing reciprocal space resolution. In addition, a set of of narrow diffuse peaks having profiles similar to thermal and phasonic diffuse scattering is present, which is only seen in high resolution patterns. The former diffuse scattering represents unresolved Bragg reflections, while the latter is due to truncation effects coming from the finite crystal size. The relevance of the findings for the understanding of real experimental diffraction patterns is discussed on the examples of diffuse scat tering from d-Al70Co 12Ni18 and i-Al64Cu23Fe 13. Finally, some criteria for distinguishing disorder diffuse scattering from artificial diffuse scattering are given. © by Oldenbourg Wissenschaftsverlag.