Diffraction studies of glass structure III. Limitations of the fourier method for polyatomic glasses

Using the scattering intensity calculated for a simple quasi-crystalline model based on the high-cristobalite structure, for which the structural correlation function is known exactly, the fourier transformation of X-ray and neutron intensity data for a polyatomic glass has been investigated. The effects of termination of the data at finite Q, quadrature interval, data normalisation and various kinds of errors are discussed. The resulting form of the distortions on the derived correlation functions, of errors in peak positions and in peak areas are described and it is shown that a variety of errors give rise to pronounced structure in the correlation function at low values of r, below the first true peak.