Does CH 5+ prefer a C2vrather than a Csstructure?

The closely related C s (1) and C 2v (3) structures of CH 5 + have been reinvestigated at many ab initio levels using MP2/6-31G .. and MP2/6-311++G(2df,2pd) geometries. The largest basis sets employed were 6-311 (3df,2p), 6-311++G(3df,3pd), and the Dunning «correlation consistent» polarized triple-split valence basis set (cc-pVTZ). Electron correlation was probed at the MP4 level, but the QCISD method was also used with the largest basis sets