  Ab initio molecular dynamics simulation is used to study the structure and
electronic properties of the liquid Ga-Se system at the three compositions
Ga$_2$Se, GaSe and Ga$_2$Se$_3$, and of the GaSe and Ga$_2$Se$_3$ crystals. The
calculated equilibrium structure of GaSe crystal agrees well with available
experimental data. The neutron-weighted liquid structure factors calculated
from the simulations are in reasonable agreement with recent neutron
diffraction measurements. Simulation results for the partial radial
distribution functions show that the liquid structure is closely related to
that of the crystals. A close similarity between solid and liquid is also found
for the electronic density of states and charge density. The calculated
electronic conductivity decreases strongly with increasing Se content, in
accord with experimental measurements.
