  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. 
Calculation of the parity and time reversal violating interaction in   ^{225}RaO