ИСТИНА

Within oscillation electron model the superconducting crystal AB is considered consisting of two subsystems for phase separation 2AB=A2+B2. The parameters q/q_ι [A_ιB] for the isotopes FeSe and q/q_ι [AB_ι] for the isotopes MgB2 are calculated. Thin FeSe films refer to 2D systems. Calculations of interaction parameter q and phase superconducting transition temperature T_c for a thin FeSe film on a SrTiO3 substrate have been carried out. 2FeSe = Fe2 + Se2, 2 SrTιO3 = Sr2 + Tι2 + 3O2, q = 2 Φ^2_FeSe/(Φ^2_Fe+Φ^2_Se+Φ^2_Sr+Φ^2_Tι+3 Φ^2_O), where Φ^2 are square plasma energy for FeSe, Fe, Se, Sr, Tι, O, respectively. From phase diagram the equation of the straight line we obtain for q = 0.47, T_c = 92.7K. Using the oscillation plasma model, known experimental data are well described.