High-resolution atomic distribution functions of disordered materials by high-energy X-ray diffraction

The atomic-scale structure of materials with different degrees of structura l disorder has been investigated by high-energy (E greater than or equal to 60 keV) X-ray diffraction. Good quality structure functions extended to wa ve vectors of magnitude Q greater than or equal to 40 Angstrom (-1) have be en obtained even in case of materials composed of weakly scattering, light atomic species. The corresponding high-resolution atomic distribution funct ions allowed fine structural features differing in as little as (0.14 Angst rom) to be resolved. In particular, the distinct Ga-As (similar to2.43 Angs trom) and In-As (2.61 Angstrom) bonds in In-Ga-As alloys have been differen tiated. The atomic-scale structure or 'restacked' WS2 has been determined a nd the presence of three distinct W-W distances occurring at 2.77, 3.27 and 3.85 Angstrom established. Finally, Si-O (similar to1.61 Angstrom), Al-O ( similar to1.75 Angstrom) and Ca-O (similar to2.34 Angstrom) bonds in calciu m aluminosilicate glasses have been differentiated and the characteristics of the respective co-ordination polyhedra revealed. (C) 2001 Elsevier Scien ce B.V. All rights reserved.