Local structures in glassy and liquid As2Se3 - an anomalous X-ray scattering study

Anomalous X-ray scattering experiments have been performed for glassy (g-) As2Se3 at room temperature and for liquid (I-) As2Se3 at 400 degreesC in or der to clarify the role of each constituent for the short- and intermediate -range order (SRO and IRO). The differential structure factors Delta S-l(Q) s close to the As and Se K edges have been obtained from a detailed analysi s. The first nearest neighbour distances around both As and Se are about 0. 24 +/- 0.02 nm for both g- and I-As2Se3, which would support the SRO model that g- and I-As2Se3 have an SRO similar to the corresponding crystal. The prepeak in S(Q) for g-As2Se3 seems to be dominated by a partial structure f actor SA,A,(Q), which reveals the existence of the As-As IRO with a correla tion length of about 0.52 nm. In I-As2Se3, however, the substitution of Se atoms into some As sites would cause a contribution in A,,S(Q) at the prepe ak position. (C) 2001 Elsevier Science B.V. All rights reserved.