  The electronic structure of the strained FeSe0.5Te0.5 superconductor has been
investigated from first principles. Our calculation results indicate that the
influence of hydrostatic, biaxial or uniaxial compressive stress on the density
of states at the Fermi level is insignificant. The overall shape of the
Fermi-surface (FS) nesting function for FeSe0.5Te0.5 at ambient pressure
resembles that of its parent compound, FeSe, but under the ab-plane compressive
strain. In these two systems, changes of their FSs under various stress
conditions are qualitatively almost the same. However, in FeSe0.5Te0.5 the
intensity of the perfect Q=(0.5,0.5)*(2\pi/a) nesting vector is more
diminished. These findings are in good agreement with former experimental data
and support the idea of spin-fluctuation mediated superconductivity in iron
chalcogenides.
