Tunneling splittings of vibrationally excited states using general instanton paths

Eraković, Mihael; Cvitaš, Marko Tomislav (2020) Tunneling splittings of vibrationally excited states using general instanton paths. Journal of Chemical Physics, 153 (13). ISSN 0021-9606

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Abstract

A multidimensional semiclassical method for calculating tunneling splittings in vibrationally excited states of molecules using Cartesian coordinates is developed. It is an extension of the theory by Mil’nikov and Nakamura [J. Chem. Phys. 122, 124311 (2005)] to asymmetric paths that are necessary for calculating tunneling splitting patterns in multi-well systems, such as water clusters. Additionally, new terms are introduced in the description of the semiclassical wavefunction that drastically improves the splitting estimates for certain systems. The method is based on the instanton theory and builds the semiclassical wavefunction of the vibrationally excited states from the ground-state instanton wavefunction along the minimum action path and its harmonic neighborhood. The splittings of excited states are thus obtained at a negligible added numerical effort. The cost is concentrated, as for the ground-state splittings, in the instanton path optimization and the hessian evaluation along the path. The method can thus be applied without modification to many mid-sized molecules in full dimensionality and in combination with on-the fly evaluation of electronic potentials. The tests were performed on several model potentials and on the water dimer.

Item Type:	Article
Uncontrolled Keywords:	instanton theory, tunnelling splittings, tunnelling dynamics, rovibrational states of molecules
Subjects:	NATURAL SCIENCES > Physics NATURAL SCIENCES > Chemistry
Divisions:	Division of Physical Chemistry
Projects:	Project title Project leader Project code Project type Svjetlo na molekulama: istraživanje spregnute elektronske i nuklearne dinamike-LightMol Nađa Došlić IP-2016-06-1142 HRZZ Provedba vrhunskih istraživanja u sklopu Znanstvenog centra izvrsnosti za kvantne i kompleksne sustave te reprezentacije Liejevih algebri-QuantiXLie Hrvoje Buljan; Pavle Pandžić KK.01.1.1.01.0004 EK
Depositing User:	Mihael Eraković
Date Deposited:	01 Oct 2020 14:17
URI:	http://fulir.irb.hr/id/eprint/5958
DOI:	10.1063/5.0024210

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