Reply to “Comment on ‘Elimination of translational and rotational motions in nuclear orbital plus molecular orbital theory’ ” [J. Chem. Phys. 123, 237101 (2005)

Abstract

The reply to “Comment on ‘Elimination of transitional and rotational motions in nuclear orbital plus molecular orbital theory’ ” [J. Chem. Phys. 122, 164101 (2005)] is discussed. Sutcliffe pointed out in his Comment that it is impossible to rigorously construct a translation- and rotation-free (TRF)-nuclear orbital plus molecular orbital (NOMO) Hamiltonian. The essential problems pointed out in the Comment undoubtedly exist and the TRF treatment for a nonrigid rotator system cannot rigorously succeed in general cases, as well as in the NOMO theory. However, the localized nuclear wave function represented by the Gaussian basis functions enables us to separate the nuclear motion into the zeroth-order rigid-body rotation and the higher-order coupling. The TRF-NOMO method adopts the unique definition of the center of mass, angular, and internal coordinates for the zeroth-order rotator. This treatment can numerically avoid the essential problems pointed out by Sutcliffe.