Section 6. Liquid semiconductors Combined X-ray and neutron diraction from binary liquids and amorphous semiconductors A.C. Barnes a, * , M.A. Hamilton a , P. Buchanan a , M.-L. Saboungi b a H.H. Wills Physics Laboratory, Royal Fort, Tyndall Avenue, Bristol BS8 1TL, UK b Materials Science Division, Argonne National Laboratory, Argonne, Illinois IL 60439, USA Abstract Neutron scattering and isotopic substitution has been established as a method of unambiguously determining the partial structure factors of binary liquid and amorphous materials. In this paper we present results of an extension of this method to include X-ray diraction as a method of enhancing the structural information obtained. We have applied a combination of two neutron diraction experiments using isotopic substitution and one X-ray diraction experiment to obtain the partial structure factors and pair distribution functions of liquid TlSe. We have applied the anomalous X-ray diraction technique to glassy PSe using the Se K-edge. The results show that the ®rst sharp diraction peak observed in this glass arises almost entirely from the P±P correlations. We have applied the combined X-ray anomalous scattering and neutron diraction technique to obtain the partial structure factors of glassy GeO 2 . The results from two independent data sets have been compared and are in good agreement. Ó 1999 Elsevier Science B.V. All rights reserved. 1. Introduction A full understanding of the structure and properties of disordered materials requires infor- mation concerning the local correlations of the atoms in the material that can be compared to theory or computer simulation. Diraction exper- iments at the total structure factor level give lim- ited information about the atomic structure of a material due to the linear combination of the partial structure factors in reciprocal space and the overlap of peaks in real space. The technique of neutron diraction and isotopic substitution (NDIS) is established as a method of determining the partial structure factors of binary molten salts, liquid metals and aqueous and non-aqueous so- lutions [1,2,8±11]. In comparison X-ray diraction is limited mainly to total structure factor mea- surements that yield more limited structural in- formation. X-ray anomalous scattering methods for determining partial structure factors have been relatively little used, largely due to the limited contrast in the scattering factors that can be ob- tained and the experimental diculties in the anomalous scattering measurements [3,4]. How- ever, with recent developments at third generation X-ray synchrotron sources, the outlook is im- proving. The possibility of combining neutron and X-ray diraction measurements to obtain partial structure factors has often been suggested but relatively little work, to our knowledge, has been published. The aim of this paper is to describe recent work that we have carried out which ex- ploits the excellent source characteristics and Journal of Non-Crystalline Solids 250±252 (1999) 393±404 www.elsevier.com/locate/jnoncrysol * Corresponding author. Tel.: +44 117 928 8701; fax: +44 117 925 5624; e-mail: a.c.barnes@bristol.ac.uk 0022-3093/99/$ ± see front matter Ó 1999 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 - 3 0 9 3 ( 9 9 ) 0 0 3 0 8 - 7