Simplified approach to the mixed time-averaging semiclassical initial value representation for the calculation of dense vibrational spectra

Abstract

We present and test an approximate method for the semiclassical calculation of vibrational spectra. The approach is based on the mixed time-averaging semiclassical initial value representation method, which is simplified to a form that contains a filter to remove contributions from approximately harmonic environmental degrees of freedom. This filter comes at no additional numerical cost, and it has no negative effect on the accuracy of peaks from the anharmonic system of interest. The method is successfully tested for a model Hamiltonian and then applied to the study of the frequency shift of iodine in a krypton matrix. Using a hierarchic model with up to 108 normal modes included in the calculation, we show how the dynamical interaction between iodine and krypton yields results for the lowest excited iodine peaks that reproduce experimental findings to a high degree of accuracy.

Protonated glycine supramolecular systems: the need for quantum dynamics

“…The semiclassical initial value representation (SC-IVR) approximation 27 – 30 of quantum dynamics has been proved to be reliable and robust. 31 – 47 Recently, we developed an SC-IVR method based on a “divide-and-conquer” strategy (DC SCIVR) to undertake the spectroscopic calculations of eqn (1). 48 The method can deal with very high dimensional molecular and supra-molecular systems, and it is very accurate when compared to available exact vibrational quantum mechanical calculations.…”

When classical trajectories get to quantum accuracy: II. The scattering of rotationally excited H2 on Pd(111)

“…(11) is the starting point of the SCIVR, 45,46,48,49 remarkably accurate for direct inelastic collisions, 45,47,50 direct collinear reactions 51,52 and molecular spectroscopy. 53,54 The interested reader will find detailed developments on SCIVR in the previously mentioned references and references therein.…”

Qual È La Più Piccola Goccia D’acqua?

“…Nel mio gruppo di ricerca (https://sites.unimi.it/ceotto/) abbiamo recentemente sviluppato dei metodi basati sulla meccanica semiclassica [5][6][7][8][9][10][11][12][13], grazie ad un finanziamento dell'European Research Council. In particolare, abbiamo esteso le teorie semiclassiche al calcolo degli spettri vibrazionali di sistemi molecolari complessi e supramolecolari [14][15][16][17][18][19][20][21]. La meccanica semiclassica, come si può comprendere dalla Fig.…”