Range of the t--J model parameters for CuO$_{2}$ plane: experimental   data constraints
  The t-J model effective hopping integral is determined from the three-band Hubbard model for the charge carriers in CuO$_{2}$ plane. For this purpose the values of the superexchange constant $J$ and the charge-transfer gap $E_{gap}$ are calculated in the framework of the three-band model. Fitting values of $J$ and $E_{gap}$ to the experimental data allows to narrow the uncertainty region of the three-band model parameters. As a result, the $t/J$ ratio of the t-J model is fixed in the range $2.4 \div 2.7$ for holes and $2.5 \div 3.0$ for electrons. Formation of the Frenkel exciton is justified and the main features of the charge-transfer spectrum are correctly described in the framework of this approach. 
V. I. Belinicher, A. L. Chernyshev, L. V. Popovich