  By means of first-principles calculations? we have probed the peculiarities
of the elecrtonic band structure and Fermi surface for the recently discovered
layered superconductor LaO0.5F0.5BiSi2 in comparison with the parent phase
LaOBiO2. The electronic factors prpmoting the transition of LaOBiS2 upon
fluorine doping to superconducting state: inter-layer charge transfer, the
evolution of the Fermi surface, and the dependence of the near-Fermi densities
of states on x for LaO1-xFxBiS2 are evaluated and discussed in comparison with
the available experiments.
