  Using the experimentally measured temperature and doping dependent structural
parameters on Ru doped BaFe$_2$As$_2$, orbital-dependent reconstruction of the
electronic structure across the magnetostructural transition is found, through
first principle simulations. Below structural transition there exists two
distinct Fe - Fe bond distances which modifies the Fe-d$_{xy}$ orbital largely
due to its planar spatial extension leading to Lifshitz transition, while the
otherwise degenerate Fe-d$_{xz}$ and d$_{yz}$ orbitals become non-degenerate,
giving rise to orbital order. The orbital order follows the temperature
dependence of orthorhombocity and is also the cause of two distinct Fe - Fe
bond distances. Doping dependent Fermi surfaces show nearly equal expansion of
both the electron and hole like Fermi surfaces whereas the hole Fermi surface
shrinks with temperature but the electron Fermi surface expands comparatively
slowly. The observed structural transition in this compound is electronic in
origin, occurs close to the Lifshitz transition whereas the suppression of the
concurrent magnetic transition is due to loss of temperature dependent nesting
of Fermi surface.
