The DFT calculations were performed of densities of states of semiconductor GaAs and magnetic semiconductor Ga0.9375Mn0.0625As. It is obtained that a part of Mn3d- states is hybridized with valence band at Fermi level. The exchange integrals of Anderson impurity model were calculated making use of atomic Hartree-Fock package and angular momentum coupling technique. Theoretical Tc of Ga0.9375Mn0.0625As obtained in the multiscale ab initio method is in reasonable agreement with experiment. The application of Hubbard parameters in DFT calculations using ultrasoft pseudopotentials is discussed.