title: Reproducing Deep Tunneling Splittings, Resonances, and Quantum Frequencies in Vibrational Spectra From a Handful of Direct Ab Initio Semiclassical Trajectories.
abstract: A time-dependent semiclassical approach for vibrational spectra calculations is shown to describe deep tunneling splittings, resonances, and quantum frequencies in multidimensional multiwell systems, by propagating a very limited number of classical trajectories. The approach is tested on ammonia by evolving eight trajectories on a full-dimensional PES. Quantum effects are reproduced, and results are in good agreement with time-independent quantum calculations. All the features are maintained when ab initio "on-the-fly" dynamics is adopted, thus demonstrating that precomputation of the PES can be avoided. The approach overcomes the typical scaling issues of quantum mechanical techniques without introducing any simplifications nor reductions of dimensionality of the problem. The proposed methodology is promising for further applications to systems of major complexity.
authors.affiliation: Department of Chemistry and Cherry L. Emerson Center for Scientific Computation, Emory University , Atlanta, Georgia 30322, United States.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Conte
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University , Cambridge, Massachusetts 02138, United States.
authors.forename: Alán
authors.initials: A
authors.lastname: Aspuru-Guzik
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Milano , via Golgi 19, 20133 Milano, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Ceotto
keywords: MC-TA-SC-IVR; ab initio on-the-fly molecular dynamics; ammonia; deep resonant tunneling; quantum vibrational spectra; semiclassical dynamics