A general formulation of the quasiclassical trajectory method for reduced-dimensionality reaction dynamics calculations. Issue 19 (3rd May 2018)

• Record Type: Journal Article
• Authors: Nagy, Tibor; Vikár, Anna; Lendvay, György
• Is Part Of: Physical chemistry chemical physics. Volume 20:Issue 19(2018)
• Page Start: 13224
• Page End: 13240
• Publication Date: 2018-05-03
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c8cp01600c
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : A black-box formalism for generating initial conditions and following trajectories in reduced-dimensionality quasiclassical trajectory calculations using arbitrary internal coordinates. Abstract : Dimension reduction by freezing the unimportant coordinates is widely used in intramolecular and reaction dynamics calculations when the solution of the accurate full-dimensional nuclear Schrödinger equation is not feasible. In this paper we report on a novel form of the exact classical internal-coordinate Hamiltonian for full and reduced-dimensional vibrational motion of polyatomic molecules with the purpose of using it in quasiclassical trajectory (QCT) calculations. The derivation is based on the internal to body-fixed frame transformation, as in thet -vector formalism, however it does not require the introduction of rotational variables to allow cancellation of non-physical rotations within the body-fixed frame. The formulas needed for QCT calculations: normal mode analysis and state sampling as well as for following the dynamics and normal-mode quantum number assignment at instantaneous states are presented. The procedure is demonstrated on the CH4, CD4, CH3 D and CHD3 isotopologs of methane using three reduced-dimensional models, which were previously used in quantum reactive scattering studies of the CH4 + X → CH3 + HX type reactions. The reduced-dimensional QCT methodology formulated this way combined with full-dimensional QCT calculations makes possible the classical validation of reduced-dimensional models that are used in the quantum mechanical description of the nuclear dynamics in reactive systems [A. Vikár et al., J. Phys. Chem. A, 2016, 120, 5083–5093].