Vibrational spectra of polyatomic molecules are often obtained from a polynomial expansion of the adiabatic potential around a minimum. For several molecules, we show that such an approximation displays an unphysical saddle point of comparatively small energy, leading to a region where the potential is negative and unbounded. This poses an upper limit for a reliable evaluation of vibrational levels. We argue that the presence of such saddle points is general.
Del Monte, A., Manini, N., Molinari, L., Brivio, G. (2005). Low-energy unphysical saddle in polynomial molecular potentials. MOLECULAR PHYSICS, 103(5), 689-696 [10.1080/00268970412331332114].
Low-energy unphysical saddle in polynomial molecular potentials
BRIVIO, GIANPAOLO
2005
Abstract
Vibrational spectra of polyatomic molecules are often obtained from a polynomial expansion of the adiabatic potential around a minimum. For several molecules, we show that such an approximation displays an unphysical saddle point of comparatively small energy, leading to a region where the potential is negative and unbounded. This poses an upper limit for a reliable evaluation of vibrational levels. We argue that the presence of such saddle points is general.
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