  The 10-electron generalized relativistic effective core potential and the
corresponding correlation spin-orbital basis sets are generated for the Ra atom
and the relativistic coupled cluster calculations for the RaO molecule are
performed. The main goal of the study is to evaluate the P,T-odd parameter X
characterized by the molecular electronic structure and corresponding to a
"volume effect" in the interaction of the ^{225}Ra nucleus Schiff moment with
electronic shells of RaO. Our final result for X(^{225}RaO) is -7532 which is
surprisingly close to that in ^{205}TlF but has different sign. The obtained
results are discussed and the quality of the calculations is analyzed. The
value is of interest for a proposed experiment on RaO [PRA 77, 024501 (2008)]
due to a very large expected Schiff moment of the ^{225}Ra nucleus.

Atomic Physics;Chemical Physics