Calculation of the PbO molecule for the electron EDM experiment. A.N. Petrov, T.A. Isaev, N.S. Mosyagin, and A.V. Titov Petersburg Nuclear Physics Institute, Gatchina, 188300, Russia The search for the electric dipole moment (EDM) of the electron, d_e, has become one of the most fundamental problems in physics. Up to now only the upper limit |d_e| < 1.6 * 10^{-27} e*cm is obtained. It was noted earlier, that the experiments on the excited a(1) [1] or B(1) [2] states of PbO allow one a detection for d_e up to three or four orders of magnitude lower than the current limit. The feature of such experiments is that the knowledge of the effective electric field, W_d, seen by an unpaired electron is required for extracting d_e from the measurements. W_d can not be obtained in an experiment, so the electronic structure calculations are required. In the present work the code for the direct configuration interaction calculation (SODCI) [3] is employed where the relativistic (spin-orbit) scheme [4] and new criteria [4,5] of the configuration selection proposed by us earlier are incorporated. Besides, the code for calculation of a one-electron density matrix with the CI wavefunction are developed. With these codes the 10-electron GRECP/SODCI calculations followed by the nonvariational one-center restoration of the four-component wavefunction in the Pb core are first performed for core properties, hyperfine and W_d constants, of the a(1) and B(1) states in PbO. In calculations of valence properties, a new ``correlated'' GRECP version was used accounting for correlations with the core electrons of Pb. The present calculations are compared with our recent relativistic coupled cluster ones [6]. The present work was supported by U.S. CRDF grant No. RP2-2339-GA-02 and RFBR grant No. 03-03-32335. A.P. is grateful to the Ministry of Education of the Russian Federation (Grant PD02-1.3-236) and to the St.Petersburg Committee on Science and Higher Education (Grant PD03-1.3-60). T.I. thanks INTAS for Grant YSF 2001/2-164. N.M. is supported in part by the scientific fellowship grant of the governor of Leningrad district and by the grant of the Russian science support foundation. [1] D. DeMille, F. Bay, J.S. Bickman, D. Kawall, D. Krause, S.E. Maxwell, and L.R. Hunter, Phys. Rev. A 61, 052507 (2000); [2] D. Egorov, J.D. Weinstein, D. Patterson, B. Friedrich, and J.M. Doyle, Phys. Rev. A 63, 030501(R) (2001). [3] R J Buenker and S Krebs, in ``Recent Advances in Multireference Methods'', ed.~by K Hirao (World Scientific, Singapore, 1999). [4] A.V.Titov and N.S.Mosyagin and A.B.Alekseyev and R.J.Buenker, Int.J.Quant.Chem., 88, 681 (2002). [5] N.S.Mosyagin and A.V.Titov and R.J.Buenker and H.-P.Liebermann and A.B.Alekseyev, Int.J.Quant.Chem., 81, 409 (2001). [6] T.A. Isaev, A.N. Petrov, N.S. Mosyagin, A.V. Titov, E. Eliav and U. Kaldor, Phys. Rev. A (Rapid Comm.), in press.