Tracing the origin of the first sharp diffraction peak (FSDP) of sodium metaphosphate glass and melt

The phenomenon of 'first sharp diffraction peaks' (FSDP) present in the dif fractograms of certain amorphous solid or liquid systems below the so-calle d main diffraction peak is studied by the use of Fourier transforms remaini ng within the diffraction theory of non-crystalline systems. Performing the inverse transformation of the reduced radial distribution functions (RDFs) in separate parts enables us to trace the origin of an FSDP - or any other features of the diffraction pattern - to real space. This means that all p ieces of information on the (disordered) structure contained by the structu re factors are comprised of the pair distribution functions too. The input of extraneous distances, layers, etc. is unnecessary and therefore misleadi ng. (C) 2000 Elsevier Science B.V. All rights reserved.