  The mechanism of formation of dome-like phase diagrams and the features of
magnetic field penetration in iron pnictides with hetero- and isovalent doping
are considered within the framework of the previously proposed model, which
assumes the local character of doping and the cluster structure of resulted
superconducting phase. It is shown that the proposed model, despite its
simplicity and neglect of the features of the electronic structure, makes it
possible not only to accurately calculate the positions of superconducting
domes on the phase diagrams of specific HTSC compounds, but also to explain the
nature and position of sharp peaks in the London penetration depth depending on
the doping level.
