Effect of the Triaxial Angular Momentum Projection on the Potential Energy Surface

The triaxial spin projection is applied to the ground state expectation value of the Hamiltonian with the monopole pairing plus quadrupole interaction. It is turned out that the restoration of exact spin value has strong triaxiality-driving effect for all of three nuclei ¹⁴²Nd, ¹⁶⁸Er and ¹⁸⁸Os, which have been regarded as the spherical, the prolate and the γ-unstable nuclei, respectively.