Ab initio determination of solid-state nanostructure

Abstract

Advances in materials science and molecular biology followed rapidly from the ability to characterize atomic structure using single crystals. Structure determination is more difficult if single crystals are not available. Many complex inorganic materials that are of interest in nanotechnology have no periodic long-range order and so their structures cannot be solved using crystallographic methods. Here we demonstrate that ab initio structure solution of these nanostructured materials is feasible using diffraction data in combination with distance geometry methods. Precise, sub-ångström resolution distance data are experimentally available from the atomic pair distribution function (PDF). Current PDF analysis consists of structure refinement from reasonable initial structure guesses and it is not clear, a priori, that sufficient information exists in the PDF to obtain a unique structural solution. Here we present and validate two algorithms for structure reconstruction from precise unassigned interatomic distances for a range of clusters. We then apply the algorithms to find a unique, ab initio, structural solution for C60 from PDF data alone. This opens the door to sub-ångström resolution structure solution of nanomaterials, even when crystallographic methods fail.

Quantum Dots: Synthesis and Characterization

“…A Debye function based full pattern fitting method has been proposed for powder diffraction data treatment [173,174]. Alternatively, pair-distribution function (PDF) analysis [175][176][177] has been recently applied to deal with XPD data collected on nanocrystals with extremely small sizes and with a negligible size distribution to extract their structure. While real-space atomic PDF makes no assumption on the periodicity of the material and evaluates both the Bragg and diffuse components of the scattering pattern, the DF method is a bottom-up direct-space method.…”

A method for diffraction-based identification of amorphous sp 2 carbon materials

“…In this approach the variation procedure is applied to positions of separate atoms. If there is no preliminary data on the structural content, the initial atomic ensemble should be taken random and the possible presence of chemical bonds between atoms may be recognized only on the final step of the algorithm (cf., e.g., identification of fullerenes in [3]). The RMC method applied to the structure refinement of the annealed C 60 fullerenes (similar material to that analyzed in this paper) enabled the authors of [4] to quantify the structure of the amorphous samples in terms of the number of angles in carbon rings.…”

Algorithm for systematic peak extraction from atomic pair distribution functions

“…Although refinement of an assumed structural model is the usual approach in modern PDF analysis, fitting individual features within the PDF remains an informative complement (Božin et al, 2010). The principal motivation for the present study is to enable the ab initio creation of structural models starting from interatomic distances extracted from peak positions and intensities in the measured PDF, as demonstrated by the recent Liga algorithm structure solution for some nanostructured materials (Juhá s et al, 2006(Juhá s et al, , 2010. In these studies the peak positions were extracted manually, making this approach impractical as a more widely used general method for nanostructure determination.…”