  The atomic, electronic structure and phonon frequencies have been calculated
in a cubic and low-temperature tetragonal SrTiO3 phases at the ab initio level.
We demonstrate that the use of hybrid exchange-correlation PBE0 functional
gives the best agreement with experimental data. The results for the standard
PBE and hybrid PBE0 are compared for the two types of basis sets: a linear
combination of atomic orbitals (LCAO, CRYSTAL09 computer code) and plane waves
(PW, VASP 5.2 code). Relation between cubic and tetragonal antiferrodistortive
(AFD) phases and the relevant AFD phase transition observed at 110 K is
discussed in terms of group theory and illustrated with analysis of calculated
soft mode frequences at the {\Gamma} and R points in the Brillouin zone. Based
on phonon calculations, the temperature dependences of the Helmholtz free
energy and heat capacity are in a good agreement with experiment.
