Defects in a disordered world: The structure of glassy GeSe2

The full set of partial structure factors for the prototypical network glas s GeSe2 was measured using the method of isotopic substitution in neutron d iffraction. The basic building block of the network is the Ge(Se-1/2)(4) te trahedron in which 34(5)% of the Ge reside in edge-sharing configurations. The intrinsic chemical order of the glass is, however, broken with a maximu m of 25(5)% Ge and 20(5)% Se being involved in homopolar bonds at distances of 2.42(2) and 2.32(2) Angstrom, respectively.