Mixed semiclassical initial value representation time-averaging propagator for spectroscopic calculations

Abstract

The recently introduced mixed time-averaging semiclassical initial value representation molecular dynamics method for spectroscopic calculations [M. Buchholz, F. Grossmann, and M. Ceotto, J. Chem. Phys. 144, 094102 (2016)] is applied to systems with up to 61 dimensions, ruled by a condensed phase Caldeira-Leggett model potential. By calculating the ground state as well as the first few excited states of the system Morse oscillator, changes of both the harmonic frequency and the anhar-monicity are determined. The method faithfully reproduces blueshift and redshift effects and the importance of the counter term, as previously suggested by other methods. Differently from previous methods, the present semiclassical method does not take advantage of the specific form of the potential and it can represent a practical tool that opens the route to direct ab initio semiclassical simulation of condensed phase systems.

“Divide and conquer” semiclassical molecular dynamics: A practical method for spectroscopic calculations of high dimensional molecular systems

“…The calculation of partial spectra representations has not only the advantage to accelerate the Monte Carlo integration by virtue of the reduced dimensionality of each subspace and to get better resolved spectra, but also simplifies the identification of each peak. Another potential application of DC SCIVR is in the field of mixed (hybrid) semiclassical methods [87,120,121] due to the possibility to assign different degrees of freedom to the different semiclassical techniques employed.…”

“…[79] In the position representation, the semiclassical propagator is a matrix whose elements are obtained as products of a complex action exponential and a stationary-phase pre-exponential factor, summed over all classical trajectories that connect the two endpoints. [41,[80][81][82][83][84][85][86][87][88] The search for these trajectories is hampered by the rigid double-boundary condition. In the SC-IVR dynamics, introduced by Miller and later also developed by Heller, Herman, Kluk, and Kay, [22,27,28,30,31,34,57,89] the propagator is instead formulated in terms of classical trajectories determined by initial condi-…”

Ab Initio Semiclassical Evaluation of Vibrationally Resolved Electronic Spectra With Thawed Gaussians

“…Time averaging has proved useful in on-the-fly simulations as a central ingredient of the multiple-coherent-states time-averaged semiclassical initial value representation (Ceotto et al, 2009a(Ceotto et al, ,b, 2011. This method is especially well suited for the determination of vibrational frequencies and prediction of vibrational spectra (Buchholz et al, 2016;Ceotto et al, 2011Gabas et al, 2017). A clever choice of the initial coherent states allows a drastic reduction of the number of trajectories required for convergence of desired spectral regions.…”

Machine learning for vibrational spectroscopy via divide-and-conquer semiclassical initial value representation molecular dynamics with application to N-methylacetamide

“…For example, a collection of +1 values allows one to enhance the zero-point energy (ZPE) signal (together with the even transitions), while a selected ϵj = −1 and the remaining ϵi≠j = +1 enhance the odd transition of the jth mode. 43 The MC SCIVR has been successfully applied to the study of several systems, [44][45][46][47][48][49][50][51][52][53][54][55] including the different conformers of the glycine amino acid. 44 To improve with respect to the harmonic initial conditions of Eq.…”