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Determination of the parameters of multidimension vibration Hamiltonian of CH 3 NH 2 from quantum chemical data
Author(s) -
Irgibaeva I. S.
Publication year - 2003
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.10648
Subject(s) - hamiltonian (control theory) , normal coordinates , ground state , amplitude , eigenvalues and eigenvectors , quantum , chemistry , quantum number , methylamine , vibration , quantum mechanics , physics , normal mode , molecule , computational chemistry , classical mechanics , mathematics , mathematical optimization , organic chemistry
Abstract The two large‐amplitude motions—NH 2 wagging and CH 3 internal rotation—take place in methylamine, CH 3 NH 2 . The complete set of potential and kinematic coupling constants, characterizing the Hamiltonian of a nonrigid molecule CH 3 NH 2 with two large‐amplitude coordinates, is derived from standard quantum chemical data for the equilibrium geometries, normal frequencies, and eigenvectors in the ground and transition states. The reconstruction of the Hamiltonian is made via the following steps: classification of the generalized coordinates according to the irreducible representations of the group of the nonrigid molecular model; linear transformation of the ground‐state normal coordinates into the frame of the transition state taking into account the Eckart conditions; and perturbative solution of the inverse vibrational problem. It is shown that the consideration of interactions of large‐amplitude vibrations with transfer ones significantly affects the parameters of 2‐D potential. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004