Liberation of H2 from (o-C6H4Me)3P—H(+) + (−)H—B(p-C6F4H)3 ion-pair: A transition-state in the minimum energy path versus the transient species in Born-Oppenheimer molecular dynamics

Models suggest BrHgONO to be the major Hg(II) species formed in the global oxidation of Hg(0), and BrHgONO undergoes rapid photolysis to produce the thermally stable radical BrHgO•. We previously used quantum chemistry to demonstrate that BrHgO• can, like OH radical, readily can abstract hydrogen atoms from sp3-hybridized carbon atoms as well as add to NO and NO2. In the present work, we reveal that BrHgO• can also add to C2H4 to form BrHgOCH2CH2•, although this addition appears to proceed with a lower rate constant than the analogous addition of •OH to C2H4. Additionally, BrHgO• can readily react with HCHO in two different ways: either by addition to the carbon or by abstraction of a hydrogen atom. The minimum energy path for the BrHgO• + HCHO reaction bifurcates, forming two pre-reactive complexes, each of which passes over a separate transition state to form a different product.

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PHYSISORPTION TO CHEMISORPTION TRANSFORMATION OF A H2 MOLECULE ON B-DOPED FULLERENE C59B

Journal of Theoretical and Computational Chemistry ◽

10.1142/s0219633611006840 ◽

2011 ◽

Vol 10 (06) ◽

pp. 839-847 ◽

Cited By ~ 4

Author(s):

CHUANJIN TIAN ◽

WENYAN ZHAO ◽

ZHIGANG WANG ◽

MINGXING JIN

Keyword(s):

Transition State ◽

Energy Barrier ◽

Minimum Energy ◽

Transformation Process ◽

Minimum Energy Path ◽

First Principle ◽

Adsorption State ◽

First Principle Calculations ◽

Dynamics Stability ◽

H2 Molecule

By first principle calculations we have explored the minimum energy path of H2 molecule dissociating on the C59B which is a system as stable as C60 . Our results show that the transformation process from physisorption state (also called nondissociation adsorption state) to the chemisorption state of the H2 molecule on the C59B surface should cross a transition state. However, the energy barrier of this reaction is very low. Therefore, the dynamics stability of the physisorption state is not high.

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BrHgO• + C2H4 and BrHgO• + HCHO in Atmospheric Oxidation of Mercury: Determining Rate Constants of Reactions with Pre-Reactive Complexes and a Bifurcation

10.26434/chemrxiv.8266733 ◽

2019 ◽

Author(s):

Khoa T. Lam ◽

Curtis J. Wilhelmsen ◽

Theodore Dibble

Keyword(s):

Hydrogen Atom ◽

Quantum Chemistry ◽

Transition State ◽

Rate Constant ◽

Rate Constants ◽

Minimum Energy ◽

Atmospheric Oxidation ◽

Minimum Energy Path ◽

Oh Radical ◽

Hydrogen Atoms

Models suggest BrHgONO to be the major Hg(II) species formed in the global oxidation of Hg(0), and BrHgONO undergoes rapid photolysis to produce the thermally stable radical BrHgO•. We previously used quantum chemistry to demonstrate that BrHgO• can, like OH radical, readily can abstract hydrogen atoms from sp3-hybridized carbon atoms as well as add to NO and NO2. In the present work, we reveal that BrHgO• can also add to C2H4 to form BrHgOCH2CH2•, although this addition appears to proceed with a lower rate constant than the analogous addition of •OH to C2H4. Additionally, BrHgO• can readily react with HCHO in two different ways: either by addition to the carbon or by abstraction of a hydrogen atom. The minimum energy path for the BrHgO• + HCHO reaction bifurcates, forming two pre-reactive complexes, each of which passes over a separate transition state to form a different product.

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Active Learning Accelerates Ab Initio Molecular Dynamics on Pericyclic Reactive Energy Surfaces

10.26434/chemrxiv.11910948 ◽

2020 ◽

Author(s):

Shi Jun Ang ◽

Wujie Wang ◽

Daniel Schwalbe-Koda ◽

Simon Axelrod ◽

Rafael Gomez-Bombarelli

Keyword(s):

Molecular Dynamics ◽

Potential Energy ◽

Transition State ◽

Potential Energy Surface ◽

Ab Initio ◽

Energy Surface ◽

Computational Cost ◽

Reactive Trajectories ◽

Dynamics Simulations ◽

Energy Surfaces

<div>Modeling dynamical effects in chemical reactions, such as post-transition state bifurcation, requires ab initio molecular dynamics simulations due to the breakdown of simpler static models like transition state theory. However, these simulations tend to be restricted to lower-accuracy electronic structure methods and scarce sampling because of their high computational cost. Here, we report the use of statistical learning to accelerate reactive molecular dynamics simulations by combining high-throughput ab initio calculations, graph-convolution interatomic potentials and active learning. This pipeline was demonstrated on an ambimodal trispericyclic reaction involving 8,8-dicyanoheptafulvene and 6,6-dimethylfulvene. With a dataset size of approximately</div><div>31,000 M062X/def2-SVP quantum mechanical calculations, the computational cost of exploring the reactive potential energy surface was reduced by an order of magnitude. Thousands of virtually costless picosecond-long reactive trajectories suggest that post-transition state bifurcation plays a minor role for the reaction in vacuum. Furthermore, a transfer-learning strategy effectively upgraded the potential energy surface to higher</div><div>levels of theory ((SMD-)M06-2X/def2-TZVPD in vacuum and three other solvents, as well as the more accurate DLPNO-DSD-PBEP86 D3BJ/def2-TZVPD) using about 10% additional calculations for each surface. Since the larger basis set and the dynamic correlation capture intramolecular non-covalent interactions more accurately, they uncover longer lifetimes for the charge-separated intermediate on the more accurate potential energy surfaces. The character of the intermediate switches from entropic to thermodynamic upon including implicit solvation effects, with lifetimes increasing with solvent polarity. Analysis of 2,000 reactive trajectories on the chloroform PES shows a qualitative agreement with the experimentally-reported periselectivity for this reaction. This overall approach is broadly applicable and opens a door to the study of dynamical effects in larger, previously-intractable reactive systems.</div>

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