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Potential energy surface

About: Potential energy surface is a research topic. Over the lifetime, 11674 publications have been published within this topic receiving 307691 citations.


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TL;DR: In this article, a theoretical ab initio study of the singlet states of salicylideneaniline (SA) is presented, where the authors show that the SA molecule in S0 and S1 states of both tautomers needs nonplanarity to stabilize.
Abstract: The theoretical ab initio studies of the singlet states of salicylideneaniline (SA) are presented. The enol, cis-keto and trans-keto tautomers were treated by the HF/6-31G* (geometries and force fields of the ground states), and the CIS (excited states), methods. For the dynamic calculations of the rates of proton transfer (PT) in S1 states, the instanton approach was applied. It was found that the SA molecule in S0 and S1 states of both tautomers needs nonplanarity to stabilize. In the ground state the corresponding angle was calculated as 44° vs the experimental value, 49°. Upon twist of the excited system, the conical intersection of (π,π*) and (n,π*) potential surfaces takes place. In enol form the absolute minimum on the S1 potential energy surface belongs to a strongly twisted (n,π*) state. In keto-form this minimum corresponds to a planar (π,π*) state, while the twisted (n,π*) has the energy ≈1055 cm−1 higher. The angles of distortion are equal 93° and 80°, for the enol and keto form, respectively....

117 citations

Journal ArticleDOI
TL;DR: In this article, the potential energy surface and properties of the transition state for reactions (1, −1) were studied by ab initio methods and used to create a transition state model of the reaction.
Abstract: The kinetics of the reactions C2H3 + H2 → H + C2H4 (1) and CH3 + H2 → H + CH4 (2) have been studied in the temperature ranges 499−947 K (reaction 1) and 646−1104 K (reaction 2) and He densities (6−18) × 1016 atoms cm-3 by laser photolysis/photoionization mass spectrometry. Rate constants were determined in time-resolved experiments as a function of temperature. Ethylene was detected as a primary product of reaction 1. Within the above temperature ranges the experimental rate constants can be represented by Arrhenius expressions k1 = (3.42 ± 0.35) × 10-12 exp(−(4179 ± 67 K)/T) cm3 molecule-1 s-1 and k2 = (1.45 ± 0.18) × 10-11 exp(−(6810 ± 102 K)/T) cm3 molecule-1 s-1. Experimental values of k2 are in agreement with the available literature data. The potential energy surface and properties of the transition state for reactions (1, −1) were studied by ab initio methods. Experimental and ab initio results of the current study were analyzed and used to create a transition state model of the reaction. The resul...

117 citations

Journal ArticleDOI
TL;DR: In this article, a direct molecular simulation (DMS) approach is used to predict the internal energy relaxation and dissociation dynamics of high-temperature nitrogen molecules by providing forces between the four atoms.
Abstract: The direct molecular simulation (DMS) approach is used to predict the internal energy relaxation and dissociation dynamics of high-temperature nitrogen. An ab initio potential energy surface (PES) is used to calculate the dynamics of two interacting nitrogen molecules by providing forces between the four atoms. In the near-equilibrium limit, it is shown that DMS reproduces the results obtained from well-established quasiclassical trajectory (QCT) analysis, verifying the validity of the approach. DMS is used to predict the vibrational relaxation time constant for N2–N2 collisions and its temperature dependence, which are in close agreement with existing experiments and theory. Using both QCT and DMS with the same PES, we find that dissociation significantly depletes the upper vibrational energy levels. As a result, across a wide temperature range, the dissociation rate is found to be approximately 4–5 times lower compared to the rates computed using QCT with Boltzmann energy distributions. DMS calculations predict a quasi-steady-state distribution of rotational and vibrational energies in which the rate of depletion of high-energy states due to dissociation is balanced by their rate of repopulation due to collisional processes. The DMS approach simulates the evolution of internal energy distributions and their coupling to dissociation without the need to precompute rates or cross sections for all possible energy transitions. These benchmark results could be used to develop new computational fluid dynamics models for high-enthalpy flow applications.

117 citations

Journal ArticleDOI
TL;DR: The mechanism of proton translocation along linear hydrogen-bonded water chains is investigated in this paper, where classical and discretized Feynman path integral molecular dynamics simulations are performed on protonated linear chains of 4, 5, and 9 water molecules.
Abstract: The mechanism of proton translocation along linear hydrogen-bonded water chains is investigated. Classical and discretized Feynman path integral molecular dynamics simulations are performed on protonated linear chains of 4, 5, and 9 water molecules. The dissociable and polarizable water model PM6 of Stillinger and co-workers is used to represent the potential energy surface of the systems. The simulations show that quantum and thermal effects are both important because the height of the barriers opposing proton transfer are strongly coupled to the configuration of the chain, which is, in turn, affected by the presence of an excess proton. For characterization of the quantum effects, the energy levels of the hydrogen nucleus located at the center of a protonated tetrameric water chain are calculated by solving the Schroedinger equation for an ensemble of configurations which were generated with path integral simulations. Analysis shows that the first excitation energies are significantly larger than the th...

117 citations

Journal ArticleDOI
TL;DR: In this paper, a theoretical study of the unimolecular dissociation resonances of HCO in the electronic ground state, X1A′, using a new ab initio potential energy surface and a modification of the log-derivative version of the Kohn variational principle for the dynamics calculations is presented.
Abstract: We present a theoretical study of the unimolecular dissociation resonances of HCO in the electronic ground state, X1A′, using a new ab initio potential energy surface and a modification of the log‐derivative version of the Kohn variational principle for the dynamics calculations. Altogether we have analyzed about 120 resonances up to an energy of ≊2 eV above the H+CO threshold, corresponding to the eleventh overtone in the CO stretching mode (v2=11). The agreement of the resonance energies and widths with recent stimulated emission pumping measurements of Tobiason et al. [J. Chem. Phys. 103, 1448 (1995)] is pleasing. The root‐mean‐square deviation from the experimental energies is only 17 cm−1 over a range of about 20 000 cm−1 and all trends of the resonance widths observed in the experiment are satisfactorily reproduced by the calculations. The assignment of the states is discussed in terms of the resonance wave functions. In addition, we compare the quantum mechanical state‐resolved dissociation rates ...

117 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023128
2022206
2021288
2020322
2019295
2018310