Nonlinear normal mode interactions in the SF(6) molecule studied with the aid of density functional theory

Some exact interactions between vibrational modes in systems with discrete symmetry can be described by the theory of the bushes of nonlinear normal modes (NNMs) [G. M. Chechin and V. P. Sakhnenko, Phys. D (Amsterdam, Neth.) 117, 43 (1998)]. Each bush represents a dynamical object conserving the energy of the initial excitation. The existence of bushes of NNMs is ensured by some group-theoretical selection rules. In G. M. Chechin et al. [Int. J. Nonlinear Mech. 38, 1451 (2003)], existence and stability of the bushes of vibrational modes in the simple octahedral model of mass points interacting via Lennard-Jones potential were investigated. In the present paper, we study these dynamical objects by the density functional theory in the SF(6) molecule, which possesses the same symmetry and structure. We have fully confirmed the results previously obtained in the framework of the group-theoretical approach and have found some properties of the bushes of NNMs.