Ab-Initio-Based Potential Energy Surfaces for Complex Molecules and Molecular Complexes

We constructed new global potential energy surface for O + O 2 → O 3 reaction. It is based on high level electronic structure theory calculations and employs fitting by permutationally invariant polynomial functions. This method of surface construction takes full advantage of permutation symmetry of three O nuclei and allows reducing dramatically the number of ab initio data points needed for accurate surface representation. New potential energy surface offers dramatic improvement over older surface of ozone in terms of dissociation energy and behavior along the minimum energy path. It can be used to refine the existing theories of ozone formation.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Global permutationally invariant potential energy surface for ozone forming reaction

Ayouz

Babikov

2013

“…21 and references therein) for high-dimensional molecular systems. 22 In particular, up to date several H + 5 surfaces are available in the literature, 10,12,20,23 with each of them based on different theoretical approaches.…”

Section: Since the Detection Of The Hmentioning

confidence: 99%

Vibrational dynamics of the ${\rm H}_5^+$H5+ and its isotopologues from multiconfiguration time-dependent Hartree calculations

Valdés

Prosmiti

Delgado‐Barrio

2012

(2010)]. The potential energy operators are constructed using the n-mode representation adapted to a four-combined mode cluster expansion, including up to seven-dimensional grids, chosen adequately to take advantage in representing the MCTDH wavefunction. An error analysis is performed to quantify the convergence of the potential expansion to reproduce the reference surfaces at the energies of interest. An extensive analysis of the vibrational ground state properties of these isotopes and comparison with the reference diffusion Monte Carlo results by Acioli et al. [J. Chem. Phys. 128, 104318 (2008)] are presented. It is found that these systems are highly delocalized, interconverting between equivalent minima through rotation and internal proton transfer motions even at their vibrational ground state. Isotopic substitution affects the zero-point energy and structure, showing preference in the arrangements of the H and D within the mixed clusters, and the most stable conformers of each isotopomer are the ones with the H in the central position. Vibrational excited states are also computed and by comparing the energies and structures predicted from the two surfaces, the effect of the potential topology on them is discussed.

“…For many-dimensional systems, due to computational limitations, the PES fitting procedure results in a sometimes drastic trade-off of computational efficiency vs accuracy of the fit. Several techniques have been developed 3 to ease these difficulties. Nowadays, first principles molecular dynamics (FPMD), or ab initio molecular dynamics (AIMD) is becoming a more attractive and useful technique to avoid computing PESs explicitly.…”

Section: Introductionmentioning

confidence: 99%

Fighting the curse of dimensionality in first-principles semiclassical calculations: Non-local reference states for large number of dimensions

Ceotto

Tantardini

Aspuru‐Guzik

2011

Semiclassical methods face numerical challenges as the dimensionality of the system increases. In the general context of the theory of differential equations, this is known as the “curse of dimensionality.” In the present manuscript, we apply the recently-introduced multi-coherent states semiclassical initial value representation (MC-SC-IVR) approach to extend the applicability of first-principles semiclassical calculations. The proposed strategy involves the use of non-local coherent states with the goal of increasing accuracy in the Fourier transforms, and on the other hand, allows for the selection of peaks of different frequencies. The ability to filter desired peaks is important for analyzing the power spectra of complex systems. The MC-SC-IVR approach allows us to solve a 19-dimensional test system and to resolve on-the-fly the power spectra of the formaldehyde molecule with very few classical trajectories.