First-principles molecular dynamics simulations are carried out to study th
e structural properties of liquid GeSe2. We use a generalized gradient appr
oximation for the exchange and correlation energy, which we find to improve
significantly upon the local density approximation in describing both the
short- and the intermediate-range structure. A very good agreement with exp
eriment is obtained for the total neutron structure factor over the entire
range of momentum transfer. In particular, the first sharp diffraction peak
(FSDP) is well reproduced. We carry out a detailed comparison between part
ial structure factors and partial pair correlations in theory and experimen
t to assess the quality of our simulation model. The short-range and interm
ediate-range structure are well described overall. However, residual differ
ences between theory and experiment, such as the absence of a FSDP in the c
oncentration-concentration structure factor, appear and are traced back to
the Ge-Ge correlations. An analysis of the bonding configurations indicates
that liquid GeSe2 is a defective network consisting of predominant Ge-cent
ered tetrahedral units, but Ge- and Se-centered triads and homopolar bonds
occur in non-negligible amounts. The number of Ge-Ge homopolar bonds and of
ordered fourfold rings compare favorably with experimental estimates. Chem
ical disorder manifests through an important percentage of Se-rich odd-memb
ered rings. We characterized the intermediate-range order by studying the r
elation between real-space distances and the FSDP. We found that this featu
re appears when correlations beyond 5 Angstrom are accounted for. The evalu
ation of bond lifetimes reflect the higher stability of Ge-Se bonds with re
spect to homopolar bonds, consistent with the predominance of tetrahedral u
nits.