The importance of the pre-exponential factor in semiclassical molecular dynamics

Liberto, Giovanni Di; Ceotto, Michele

doi:10.1063/1.4964308

Cited by 41 publications

(50 citation statements)

References 123 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…12,92 Semiclassical methods in applications to much smaller molecules such as ammonia 66 or H 2 O 54 have shown small mean absolute errors (38 and 20 cm –1 respectively) with respect to exact quantum calculations. However, exact quantum mechanical results are not available for glycine and a straightforward quantitative comparison between the reported data is not possible, since DVPT2 studies employed a different basis set from ours, and experimental spectra always come with some uncertainties in their interpretation.…”

Section: Resultsmentioning

confidence: 99%

On-the-Fly ab Initio Semiclassical Calculation of Glycine Vibrational Spectrum

Gabas

Conte

Ceotto

2017

J. Chem. Theory Comput.

Self Cite

View full text Add to dashboard Cite

We present an on-the-fly ab initio semiclassical study of vibrational energy levels of glycine, calculated by Fourier transform of the wavepacket correlation function. It is based on a multiple coherent states approach integrated with monodromy matrix regularization for chaotic dynamics. All four lowest-energy glycine conformers are investigated by means of single-trajectory semiclassical spectra obtained upon classical evolution of on-the-fly trajectories with harmonic zero-point energy. For the most stable conformer I, direct dynamics trajectories are also run for each vibrational mode with energy equal to the first harmonic excitation. An analysis of trajectories evolved up to 50 000 atomic time units demonstrates that, in this time span, conformers II and III can be considered as isolated species, while conformers I and IV show a pretty facile interconversion. Therefore, previous perturbative studies based on the assumption of isolated conformers are often reliable but might be not completely appropriate in the case of conformer IV and conformer I for which interconversion occurs promptly.

show abstract

Section: Resultsmentioning

confidence: 99%

On-the-Fly ab Initio Semiclassical Calculation of Glycine Vibrational Spectrum

Gabas

Conte

Ceotto

2017

J. Chem. Theory Comput.

Self Cite

View full text Add to dashboard Cite

show abstract

“…The time-averaging procedure (in separable approximation) acts as a filter on rapidly oscillating phase contributions, thus strongly dampening noise in the resulting spectra, while still retaining accuracy on the position of the spectral peaks. Within this formalism it was possible to reproduce vibrational spectra of small molecules by evolving roughly only one thousand classical trajectories per degree of freedom, [73][74][75][76][77][78] also demonstrating that it does not suffer from ZPE leakage, 79 and that the cost of evaluating the Hessian can be reduced by employing a database. 80 With a careful choice of initial conditions, it is even possible to employ a single classical trajectory per sought spectral peak, via the Multiple Coherent State (MC SCIVR) approach.…”

Section: A Semiclassical Cartesian Propagatormentioning

confidence: 99%

“…(6). A number of approaches has been devised to tackle this issue, including the use of approximate C t , 76 or the use of the original Eq. (11) and rejecting the trajectories such that 1 − M T M ≥ ǫ, with the arbitrary threshold ǫ usually in the range 10 −5 -10 −3 .…”

Section: E Trajectory Length and Phase Space Sampling Criteriamentioning

confidence: 99%

Reduced rovibrational coupling Cartesian dynamics for semiclassical calculations: Application to the spectrum of the Zundel cation

Bertaina

Liberto

Ceotto

2019

The Journal of Chemical Physics

Self Cite

View full text Add to dashboard Cite

We study the vibrational spectrum of the protonated water dimer, by means of a divide-and-conquer semiclassical initial value representation of the quantum propagator, as a first step in the study of larger protonated water clusters. We use the potential energy surface from [Huang et al., J. Chem. Phys. 122, 044308 (2005)]. To tackle such an anharmonic and floppy molecule, we employ fully Cartesian dynamics and carefully reduce the coupling to global rotations in the definition of normal modes. We apply the time-averaging filter and obtain clean power spectra relative to suitable reference states, that highlight the spectral peaks corresponding to the fundamental excitations of the system. Our trajectory-based approach allows us for physical interpretation of the very challenging proton transfer modes. We find that it is important, for such a floppy molecule, to selectively avoid to initially excite lower energy modes, in order to obtain cleaner spectra. The estimated vibrational energies display a mean absolute error (MAE) of ∼ 29cm −1 with respect to available Multi-Configuration time-dependent Hartree calculations and MAE ∼ 14cm −1 when compared to the optically active experimental excitations of the Ne-tagged Zundel cation. The reasonable scaling in the number of trajectories for Monte Carlo convergence is promising for applications to higher dimensional protonated cluster systems.The Zundel cation is the most representative member of the family of protonated water clusters, towards which many computational efforts are being devoted, mainly motivated by a flourishing of experimental results, 11-16 and the request for higher accuracy. [17][18][19][20][21] In this respect, this molecule is a prototypical example that has been tackled by various approaches, given the great biological relevance of the charge transport mechanism in aqueous solutions. [22][23][24][25][26][27] On the experimental side, the vibrational spectrum of the Zundel cation has been investigated by infrared multiphoton photodissociation spectroscopy 28,29 and noble gases predissociation spectroscopy, in particular Argon and Neon. [30][31][32] The theoretical literature about the vibrational spectrum of the Zundel cation is quite vast, since its strong anharmonicity provides the ideal test-bed for theoretical methods. The PES computed at the level of coupled cluster theory and devised in Ref. 33, has been employed by a plethora of methods for vibrational calculations, such as vibrational configuration interaction (VCI), 34 diffusion Monte Carlo, 32,35 classical molecu-

show abstract

“…[16,59] A different way to tackle the problem is by approximating or regularizing the prefactor. [60][61][62][63] However, none of these approaches is able to provide a way to restrict the semiclassical calculation to non-chaotic trajectories beforehand.…”

Section: Theoretical and Computational Detailsmentioning

confidence: 99%

Improved semiclassical dynamics through adiabatic switching trajectory sampling

Conte

Parma

Aieta

et al. 2019

The Journal of Chemical Physics

Self Cite

View full text Add to dashboard Cite

We introduce an improved semiclassical dynamics approach to quantum vibrational spectroscopy. In this method, a harmonic-based phase space sampling is preliminarily driven toward non-harmonic quantization by slowly switching on the actual potential. The new coordinates and momenta serve as initial conditions for the semiclassical dynamics calculation, leading to substantial decrease in the number of chaotic trajectories to deal with. Applications are presented for model and molecular systems of increasing dimensionality characterized by moderate or high chaoticity. They include a bidimensional Henon-Heiles potential, water, formaldehyde, and methane. The method improves accuracy and precision of semiclassical results and it can be easily interfaced with all pre-existing semiclassical theories.

show abstract

The importance of the pre-exponential factor in semiclassical molecular dynamics

Cited by 41 publications

References 123 publications

On-the-Fly ab Initio Semiclassical Calculation of Glycine Vibrational Spectrum

On-the-Fly ab Initio Semiclassical Calculation of Glycine Vibrational Spectrum

Reduced rovibrational coupling Cartesian dynamics for semiclassical calculations: Application to the spectrum of the Zundel cation

Improved semiclassical dynamics through adiabatic switching trajectory sampling

Contact Info

Product

Resources

About