Chemical Dynamics Simulations of Benzene Dimer Dissociation

Ma, Xiaochu; Paul, Amit Kumar; Hase, William L.

doi:10.1021/acs.jpca.5b03897

Cited by 27 publications

(83 citation statements)

References 59 publications

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“…47 The OPLS potential gives an overall good description of the benzene-benzene interaction. 48 The geometry for global potential energy minima of benzene-dimer is tilted-T, which is in excellent agreement with CCSD(T)/CBS calculations. 48,49 The OPLS Bz-Bz center-of-mass distance is 4.93 Å, whereas the CCSD(T)/CBS value is 4.96 Å.…”

Section: Simulation Methodssupporting

confidence: 72%

“…48 The geometry for global potential energy minima of benzene-dimer is tilted-T, which is in excellent agreement with CCSD(T)/CBS calculations. 48,49 The OPLS Bz-Bz center-of-mass distance is 4.93 Å, whereas the CCSD(T)/CBS value is 4.96 Å. Moreover, the energy that OPLS model gives for the potential energy minimum is -2.32 kcal/mol compared to the CCSD(T)/CBS value of -2.84 kcal/mol.…”

Section: Simulation Methodssupporting

confidence: 72%

“…Two simultaneous criteria were used to identify complex formation between Bz molecules: i.e. the distance between the centers-of-mass of two Bz molecules is less than 10 Å (the equilibrium distance between Bz molecules is 4.93 Å for the Bz-dimer); 48 and the two Bz molecules retain a distance less than 10 Å for at least 10 ps. The orientation averaged potential energy curve as done in a previous work 48 showed a potential energy of -0.039 kcal/mol when the centers-of-mass separation between two Bz is 10 Å (see Fig.…”

Section: A Atomistic Dynamics and Molecular Energies For The N2/c6h6 Bath Simulation 1 Complexes Of The Benzene Moleculesmentioning

confidence: 99%

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Comparison of intermolecular energy transfer from vibrationally excited benzene in mixed nitrogen–benzene baths at 140 K and 300 K

Ahamed

Kim

Paul

et al. 2020

The Journal of Chemical Physics

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Gas phase Intermolecular Energy Transfer (IET) is a fundamental component of accurately explaining the behavior of gas phase systems in which the internal energy of particular modes of molecules is greatly out of equilibrium. In this work, chemical dynamics simulations of mixed benzene/N2 baths with one highly vibrationally excited benzene molecule (Bz*) are compared to experimental results at 140 K. Two mixed bath models are considered. In one, the bath consists of 190 N2 and 10 Bz, whereas in the other bath 396 N2 and 4 Bz are utilized. The results are compared to 300 K simulations and experiments, revealing that Bz*-Bz vibration-vibration (V-V) IET efficiency increased at low temperatures consistent with longer lived "chattering" collisions at lower temperatures. In the simulations, at the Bz* excitation energy of 150 kcal/mol, the averaged energy transferred per collision, < Ec>, for Bz*-Bz collisions is found ~2.4 times larger in 140 K than in 300 K bath, whereas this value is ~1.3 times lower for Bz*-N2 collisions. The overall < Ec>, for all collisions, is found to be almost two times larger at 140 K compared to the one obtained from the 300 K bath. Such an enhancement of IET efficiency at 140 K is qualitatively consistent with the experimental observation. However, the possible reasons for not attaining a quantitative agreement are discussed. These results imply that the bath temperature and molecular composition as well as the magnitude of vibrational energy of a highly vibrationally excited molecule can shift the overall time scale of rethermalization.

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Section: Simulation Methodssupporting

confidence: 72%

Section: Simulation Methodssupporting

confidence: 72%

Section: A Atomistic Dynamics and Molecular Energies For The N2/c6h6 Bath Simulation 1 Complexes Of The Benzene Moleculesmentioning

confidence: 99%

See 1 more Smart Citation

Comparison of intermolecular energy transfer from vibrationally excited benzene in mixed nitrogen–benzene baths at 140 K and 300 K

Ahamed

Kim

Paul

et al. 2020

The Journal of Chemical Physics

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“…27 The C 6 H 6 /C 6 H 6 intermolecular potential is represented by the Optimized Potentials for Liquid Simulations (OPLS) model. 34 The OPLS global minimum for the benzene dimer has a T-shaped geometry with a binding energy of 2.32 kcal/mol, 35 whereas a recent CCSD(T)/CBS calculation predicts a similar geometry and a binding energy of 2.84 kcal/mol. 36 An experimental study gives ∼2.9 kcal/mol.…”

Section: Experiments and Simulation Methodsmentioning

confidence: 99%

Non-statistical intermolecular energy transfer from vibrationally excited benzene in a mixed nitrogen-benzene bath

Paul

West

Winner

et al. 2018

The Journal of Chemical Physics

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A chemical dynamics simulation was performed to model experiments [N. A. West et al., J. Chem. Phys. 145, 014308 (2016)] in which benzene molecules are vibrationally excited to 148.1 kcal/mol within a N2-benzene bath. A significant fraction of the benzene molecules are excited, resulting in heating of the bath, which is accurately represented by the simulation. The interesting finding from the simulations is the non-statistical collisional energy transfer from the vibrationally excited benzene C6H6* molecules to the bath. The simulations find that at ∼10−7 s and 1 atm pressure there are four different final temperatures for C6H6* and the bath. N2 vibration is not excited and remains at the original bath temperature of 300 K. Rotation and translation degrees of freedom of both N2 and C6H6 in the bath are excited to a final temperature of ∼340 K. Energy transfer from the excited C6H6* molecules is more efficient to vibration of the C6H6 bath than its rotation and translation degrees of freedom, and the final vibrational temperature of the C6H6 bath is ∼453 K, if the average energy of each C6H6 vibration mode is assumed to be RT. There is no vibrational equilibration between C6H6* and the C6H6 bath molecules. When the simulations are terminated, the vibrational temperatures of the C6H6* and C6H6 bath molecules are ∼537 K and ∼453 K, respectively. An important question is the time scale for complete energy equilibration of the C6H6* and N2 and C6H6 bath system. At 1 atm and 300 K, the experimental V-T (vibration-translation) relaxation time for N2 is ∼10−4 s. The simulation time was too short for equilibrium to be attained, and the time for complete equilibration of C6H6* vibration with translation, rotation, and vibration of the bath was not determined.

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“…21,22 In addition to information on fragmentation products and mechanisms, chemical dynamics can be used to obtain kinetic informations on unimolecular dissociation. In particular, from time decay of the initial population it is possible to obtain rate constants 9,10,16,18 and in some case threshold energies, via a correspondence between classical microcanonical RRKM expression (called also RRK theory) and temperature dependence of rate constant which assumes an Arrhenius-like form. These dynamics are purely newtonian, and thus rate constants are classical and anharmonic -the anharmonicity comes directly since the simulations are done on-the-fly on the full potential energy surface which is not harmonic.…”

Section: Introductionmentioning

confidence: 99%

On the Use of Quantum Thermal Bath in Unimolecular Fragmentation Simulations

Spezia¹,

Dammak²

2019

Preprint

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<div> <div> <div> <p>In the present work we have investigated the possibility of using the Quantum Thermal Bath (QTB) method in molecular simulations of unimolecular dissociation processes. Notably, QTB is aimed in introducing quantum nuclear effects with a com- putational time which is basically the same as in newtonian simulations. At this end we have considered the model fragmentation of CH4 for which an analytical function is present in the literature. Moreover, based on the same model a microcanonical algorithm which monitor zero-point energy of products, and eventually modifies tra- jectories, was recently proposed. We have thus compared classical and quantum rate constant with these different models. QTB seems to correctly reproduce some quantum features, in particular the difference between classical and quantum activation energies, making it a promising method to study unimolecular fragmentation of much complex systems with molecular simulations. The role of QTB thermostat on rotational degrees of freedom is also analyzed and discussed. </p> </div> </div> </div>

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Chemical Dynamics Simulations of Benzene Dimer Dissociation

Cited by 27 publications

References 59 publications

Comparison of intermolecular energy transfer from vibrationally excited benzene in mixed nitrogen–benzene baths at 140 K and 300 K

Comparison of intermolecular energy transfer from vibrationally excited benzene in mixed nitrogen–benzene baths at 140 K and 300 K

Non-statistical intermolecular energy transfer from vibrationally excited benzene in a mixed nitrogen-benzene bath

On the Use of Quantum Thermal Bath in Unimolecular Fragmentation Simulations

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