Breakdown of intermediate-range order in liquid GeSe2 at high temperatures

The structure of Liquid GeSe2 at T = 1373 K has been investigated by first- principles molecular dynamics. The calculated total neutron structure facto r is in good agreement with recent experimental data. We found that the dis appearance with increasing temperature of the first sharp diffraction peak (FSDP) in the total neutron structure factor is due to an increase of short -range chemical disorder. At T = 1373 K various bonding configurations coex ist in close amounts, such as the Ge-GeSe3, Ge-GeSe2 and Se-SeGe2 motifs. T his contrasts with the behaviour of liquid GeSe2 at T = 1050 K, for which m ore than half of the Ge atoms are four-fold coordinated to Se atoms in regu lar GeSe4 tetrahedra. Our result correlates the appearance of the FSPD in d isordered AX(2) network-forming materials to the predominant presence of AX (4) subunits.