Novel feasible approach to refinement of atomic-scale structure of complex disordered systems

There are still many unknown problems related to the structure of amorphous materials, because the X-ray diffraction technique has some limitations in the case of disordered systems. A research team led by Dr. A. L. Goodwin (Oxford University, UK) recently reported a new elegant general scheme to solve the structure by successfully demonstrating its application to molecular C₆₀, a-Si, and a-SiO₂. The team proposes to employ the information gained in spectroscopic experiments (such as EXAFS, Raman, NMR etc) regarding the number and distribution of atomic environments. The idea is that such information can be used as a valuable constraint in the refinement of the atomic-scale structures of nanostructured or amorphous materials from the pair distribution function (PDF), which is obtained by Fourier transform of the X-ray diffraction pattern. Although a conventional reverse Monte Carlo (RMC) approach is not always successful in obtaining the correct structure solution, the team showed that such difficulties can be removed by including the above variance term. For more information, see the paper, "Structure Determination of Disordered Materials from Diffraction Data", M. J. Cliffe et al., Phys. Rev. Lett. 104, 125501 (2010).