  The effect of deformation on the two-neutrino double decay (2nbb-decay) for
ground state transition 76Ge -> 76Se is studied in the framework of the
deformed QRPA with separable Gamow-Teller residual interaction. A new
suppression mechanism of the 2nbb-decay matrix element based on the difference
in deformations of the initial and final nuclei is included. An advantage of
this suppression mechanism in comparison with that associated with ground state
correlations is that it allows a simultaneous description of the single beta
and the 2nbb-decay. By performing a detail calculation of the 2nbb-decay of
76Ge, it is found that the states of intermediate nucleus lying in the region
of the Gamow-Teller resonance contribute significantly to the matrix element of
this process.
