A classical molecular dynamics study of recombination reactions in a microporous solid

Delogu, Francesco; Demontis, Pierfranco; Suffritti, Giuseppe Baldovino; Tilocca, Antonio

doi:10.1063/1.476840

Cited by 9 publications

(12 citation statements)

References 46 publications

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“…This is evident from the vibrational spectra reproduced by the present harmonic model. 5 Therefore the guest-host vibrational coupling could determine a more effective energy exchange between the reaction coordinate and the silicalite framework. In order to check this hypothesis the total energy along the reaction coordinate, defined as…”

Section: Resultsmentioning

confidence: 99%

“…We verified that larger cells ͑up to 2304 atoms͒ give rise to negligible differences from the present results. Simulations with a liquid solvent, consisting of 256 LJ spheres modeling tetrachloromethane, 5 were carried out in the same conditions.…”

Section: Model Methods and Calculationsmentioning

confidence: 99%

“…We then proceeded with the study of a dissociation-recombination reaction in silicalite. [4][5][6] Such kind of processes, exploiting many of the specific properties of zeolites, result particularly suitable as a starting point to obtain comparative information on the catalytic activity of different zeolitic hosts. Radical processes are usually not activated, thus a statistically meaningful number of reactive trajectories may be easily generated and examined by dissociating a stable molecule in different initial conditions and following its subsequent dynamics.…”

Section: Computer Simulationsmentioning

confidence: 99%

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Molecular dynamics simulation of an activated transfer reaction in zeolites

Demontis

Suffritti

Tilocca

1999

The Journal of Chemical Physics

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The activated transfer of a light particle between two heavier species in the micropores of silicalite and ZK4 zeolites has been studied through molecular dynamics ͑MD͒ simulations. A three-body potential controls the exchange of the light particle between the heavier ones; an effective barrier of a few k B T separates the two stable regions corresponding to symmetric ''reactant'' and ''product'' species. Harmonic forces always retain the reactants at favorable distances so that in principle only the energetic requirement must be fulfilled for the transfer to occur. The rate constant for the process ͑obtained from a correlation analysis of equilibrium MD trajectories͒ decreases by more than one order of magnitude when the barrier height is increased from 2k B T to 5k B T following an Arrhenius-type behavior. The transfer rates are always lower in ZK4. When the reaction is studied in a liquid solvent the calculated rate constants are closer to those obtained in silicalite. Since with this model the diffusive approach of the reactants is almost irrelevant on the reactive dynamics, only the different ability of each environment to transfer the appropriate energy amount to the reactants and then promote the barrier passage could be invoked to explain the observed behavior. We found that structural, rather than energetic, effects are mainly involved on this point. The lower efficiency of ZK4 seems to arise from the frequent trapping of the reactive complex in the narrow ZK4 windows in which the transfer is forbidden and from the weaker interaction of the reactive complex with the host framework compared to silicalite.

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Section: Resultsmentioning

confidence: 99%

Section: Model Methods and Calculationsmentioning

confidence: 99%

Section: Computer Simulationsmentioning

confidence: 99%

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Molecular dynamics simulation of an activated transfer reaction in zeolites

Demontis

Suffritti

Tilocca

1999

The Journal of Chemical Physics

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“…The USPP for O, H, and P were generated using the USPP 7.3 pseudopotential program with a scalar-relativistic calculation, [27] whereas the USPP for Ca and Na were taken from the standard Quantum-ESPRESSO distribution. [28] The accuracy and transferability of the Na, Ca, and O pseudopotentials were tested by comparing the optimized structures of several molecules containing these atoms with the corresponding experimental values, [20] whereas for phosphorus the optimized structure and the hydration energies of phosphate species calculated with the USPP-PW approach were compared with the results obtained from an all-electron calculation using the DMol [3] code, [29] the PBE functional and the double-numeric-polarized basis sets on all atoms. [30] The electronic wavefunctions were expanded in a plane wave (PW) basis set with a kinetic energy cutoff of 40 Ry, and k-sampling was restricted to the G point of the Brillouin zone.…”

Section: Methodology Computational Detailsmentioning

confidence: 99%

An Ab Initio Molecular Dynamics Study of Bioactive Phosphate Glasses

2010

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First principles molecular dynamics simulations of ternary phosphate‐based glasses P2O5CaONa2O (PBGs) have been carried out in order to provide an accurate description of the local structure and properties of these important materials for biomedical applications. The structures of PBGs with compositions (P2O5)0.45(CaO)x(Na2O)0.55 − x (x = 0.30, 0.35, and 0.40) were generated using a full ab initio molecular dynamics melt‐and‐quench procedure. The analysis of the structure of the glasses at 300 K shows the prevalence of the metaphosphate Q2 and pyrophosphate Q1 species, whereas the number of Q3 units, which constitute the three‐dimensional phosphate network, significantly decreases with the increase in calcium content in the glass. Calculation of the pair and angular distribution functions suggests that the rigidity of the phosphate tetrahedral glass network increases with the concentration of calcium, an observation which is interpreted in terms of the tendency of Ca2+ to be a stronger coordinator than sodium.

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“…Recently 37 we applied MD simulations to the study of the recombination reaction between two photodissociated atoms occurring in a silicalite-type zeolite and in a liquid solvent. The model and the method adopted there are the same used in the present work.…”

Section: Computational Model and Detailsmentioning

confidence: 99%

Recombination Reactions and Diffusive Properties of Diatomic Molecules in Two Different Microporous Structures: Silicalite and ZK4

1999

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Computer simulations of the dissociation-recombination reaction of diatomic molecules have been carried out in the pore networks of the zeolites silicalite and ZK4. This kind of processes can provide interesting insights into the effect of the confinement on the reaction dynamics. The diffusion of the species involved in the recombination processes has been separately investigated through equilibrium simulations. Considerable differences between silicalite and ZK4, both in the recombination probability and in the relaxation rate of excited molecules, as well as in the diffusive properties, are discussed and interpreted on the basis of the different properties of the two environments.

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A classical molecular dynamics study of recombination reactions in a microporous solid

Cited by 9 publications

References 46 publications

Molecular dynamics simulation of an activated transfer reaction in zeolites

Molecular dynamics simulation of an activated transfer reaction in zeolites

An Ab Initio Molecular Dynamics Study of Bioactive Phosphate Glasses

Recombination Reactions and Diffusive Properties of Diatomic Molecules in Two Different Microporous Structures: Silicalite and ZK4

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