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Communicated by Philip H. Bucksbaum, Stanford University, Menlo Park, CA, May 21, 2009 (received for review February 25, 2009)
Abstract
We explore the different local symmetries in colloidal glasses beyond the standard pair correlation analysis. Using our newly developed X-ray cross correlation analysis (XCCA) concept together with brilliant coherent X-ray sources, we have been able to access and classify the otherwise hidden local order within disorder. The emerging local symmetries are coupled to distinct momentum transfer (Q) values, which do not coincide with the maxima of the amorphous structure factor. Four-, 6-, 10- and, most prevalently, 5-fold symmetries are observed. The observation of dynamical evolution of these symmetries forms a connection to dynamical heterogeneities in glasses, which is far beyond conventional diffraction analysis. The XCCA concept opens up a fascinating view into the world of disorder and will definitely allow, with the advent of free electron X-ray lasers, an accurate and systematic experimental characterization of the structure of the liquid and glass states.
Footnotes
- 1To whom correspondence should be addressed. E-mail: desy-director{at}desy.de
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Author contributions: P.W., V.B., and H.D. designed research; P.W., C.G., T.A., A.D., F.Z., and G.G. performed research; C.G., T.D., and A.D.O. analyzed data; and P.W., A.D.O., and H.D. wrote the paper.
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The authors declare no conflict of interest.
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This article contains supporting information online at www.pnas.org/cgi/content/full/0905337106/DCSupplemental.
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↵* A formalism, which is applicable only to highly diluted solutions studied with incoherent radiation, was developed in refs. 17 and 18 (see also ref. 10).
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↵† The observation of odd symmetries appears to be in conflict with Friedel's law (I(−Q) = I(Q)), which holds for any plane in reciprocal space that intersects the origin. The observation of odd symmetries in our scheme is due to the deviation from the far-field (Fraunhofer) limit (13), because the sample is located as close as 20 cm to the 10-μm entrance slit, thereby adding an imaginary part to the phase factor of each particle.
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Freely available online through the PNAS open access option.
X-ray cross correlation analysis uncovers hidden local symmetries in disordered matter
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