Study of non-reactive scattering from graphene using molecular beam experiments and molecular dynamics

Mehta, Neil A.; Levin, Deborah A.; Murray, Vanessa J.; Minton, Timothy K.

doi:10.1063/1.4967614

Cited by 10 publications

(19 citation statements)

References 13 publications

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“…The temperature of the sample surface (T s ) was held at 677 K. Previous results from our group have demonstrated that HOPG is free of contamination at this temperature despite the relatively high operating pressure (2 × 10 −6 Torr) in the main scattering chamber. 6,16,22 The extremely narrow angular distributions observed for GLY, presented in section 4, confirm that the surface is clean.…”

Section: Experimental Methodssupporting

confidence: 59%

“…This trend is similar to that of N 2 and O 2 scattering from HOPG. 16,17 For H 2 O and CO 2 , the IS mechanism dominates at when θ i = 30 and 45°, and the EIS mechanism becomes important when θ i = 70°. In contrast, EIS is dominant for GLY at both 45 and 70°.…”

Section: Computational Resultsmentioning

confidence: 99%

“…Similar results have also been observed for H 2 O scattering from graphite (⟨E i ⟩ = 3.38 kJ mol −1 ; θ i = 40°; T s = 300 K) and N 2 scattering from HOPG (⟨E i ⟩ = 30.3 and 67.9 kJ mol −1 ; θ i = 30, 45, and 70°; T s = 677 K). 16,46 This unusual result arises because the normal incidence energy of H 2 O is low (E n,i = 4.55 kJ mol −1 ; θ i = 70°) in comparison to the energy of the surface (2RT s = 11.3 kJ mol −1 ). Consequently, energy is transferred from the hot surface into the translational energy of the molecule along the surface normal as is evident by the E̅ ⊥ > 100% in Table 5.…”

Section: Discussionmentioning

confidence: 99%

“…The experiments were conducted with the use of a crossed molecular beams machine reconfigured for beam-surface scattering. A description of this apparatus has been presented in detail in earlier publications, 6,16 and only the relevant information will be presented here. A continuous molecular beam of H 2 O, CO 2 , and GLY seeded in He was directed at a sample of ZYA quality HOPG (Momentive Inc., mosaic spread of 0.4 ± 0.1°).…”

Section: Experimental Methodsmentioning

confidence: 99%

“…The surface model employed in this study was used recently to study the scattering of N 2 from HOPG. 16 The experimental surface temperature (T s = 677 K) was simulated with the initial conditions that the velocities of surface atoms, except for the bottom layer, is assigned with a Maxwell−Boltzmann distribution at 677 K, followed by 20 ps equilibration with an isobaric−isothermal (NPT) ensemble, in which the periodic cell was held at a constant pressure of 1 atm using the Berendsen barostat with a damping constant of 50 fs and a Berendsen thermostat with a coupling of 10 fs. 33 This equilibration step was followed by an extra 30 ps microcanonical (constant number, volume, and energy, NVE) MD simulation.…”

Section: Methodsmentioning

confidence: 99%

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Scattering Dynamics of Glycine, H₂O, and CO₂ on Highly Oriented Pyrolytic Graphite

Murray

Zhou

et al. 2019

J. Phys. Chem. C

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The dynamics of H2O, CO2, and glycine (GLY) colliding with highly oriented pyrolytic graphite (HOPG) have been explored with beam-surface scattering techniques and molecular dynamics (MD) simulations that were carried out using a reactive force field. A supersonic, continuous molecular beam containing H2O, CO2, and GLY with incidence translational energies of 38.9, 87.5, and 149.5 kJ mol–1, respectively, was directed at an HOPG surface held at a temperature of 677 K. Angular and translational energy distributions of the inelastically scattered molecules were derived from time-of-flight distributions collected with a rotatable mass spectrometer employing electron bombardment ionization. The experimental results indicated that H2O and CO2 retained their incident parallel energy during the gas–surface interaction. The scattering dynamics of GLY were more complicated, as a substantial fraction of the molecules exchanged a significant amount of energy during the gas–surface interaction but did not come into thermal equilibrium with the surface. The MD simulations revealed that each of the three molecules scattered from the surface via three mechanisms, which could be distinguished by the number of inner turning points (ITPs) within the trajectory: impulsive scattering (one ITP), extended impulsive scattering (two or more ITPs), and trapping (molecule remained on the surface when the simulation was terminated). The results show that the scattering dynamics are heavily dependent on the strength of molecule–surface interaction. Molecules with a stronger attraction tend to have longer residence times on the surface and consequently experience more translational energy transfer and vibrational excitation. This study is part of a broader effort focused on evaluating the efficacy of a funnel-like neutral-gas concentrator designed for increasing the flux of gas into a mass spectrometer intended for the characterization of tenuous planetary atmospheres. Complex scattering dynamics, such as those observed in this study, must be considered carefully when designing a neutral-gas concentrator that can collect a variety of molecules.

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Section: Experimental Methodssupporting

confidence: 59%

Section: Computational Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 3 more Smart Citations

Scattering Dynamics of Glycine, H₂O, and CO₂ on Highly Oriented Pyrolytic Graphite

Murray

Zhou

et al. 2019

J. Phys. Chem. C

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Development and validation of a finite-rate model for carbon oxidation by atomic oxygen

Swaminathan‐Gopalan

Borner

Murray

et al. 2018

Carbon

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Chemical Dynamics Simulation of Low Energy N₂ Collisions with Graphite

et al. 2017

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A chemical dynamics simulation was performed to study low energy collisions between N 2 and a graphite surface. The simulations were performed as a function of collision energy (6.34 and 14.41 kcal/mol), incident polar angle (20−70°) and random azimuthal angle. The following properties were determined and analyzed for the N 2 + graphite collisions:(1) translational and rotational energy distributions of the scattered N 2 ; (2) distribution of the final polar angle for the scattered N 2 ; (3) number of bounces of N 2 on the surface before scattering. Direct scattering with only a single bounce is dominant for all incident angles. Scattering with multiple collisions with the surface becomes important for incident angles far from the surface normal. For trajectories that desorb, the parallel component of the N 2 incident energy is conserved due to the extremely short residence times of N 2 on the surface. For scattering with an incident energy of 6.34 kcal/mol, incident polar angle of 40°, and final polar angle of 50°the percentage incident energy loss is 29% from the simulations, while the value is 27% for a hard cube model used to interpret experiment (J. Phys.: Condes. Matter 2012, 24, 354001). The incident energy is primarily transferred to surface vibrational modes, with a very small fraction transferred to N 2 rotation. An angular dependence is observed for the energy transfer, with energy transfer more efficient for incident angles close to surface normal.

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Study of non-reactive scattering from graphene using molecular beam experiments and molecular dynamics

Cited by 10 publications

References 13 publications

Scattering Dynamics of Glycine, H₂O, and CO₂ on Highly Oriented Pyrolytic Graphite

Scattering Dynamics of Glycine, H₂O, and CO₂ on Highly Oriented Pyrolytic Graphite

Development and validation of a finite-rate model for carbon oxidation by atomic oxygen

Chemical Dynamics Simulation of Low Energy N₂ Collisions with Graphite

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Study of non-reactive scattering from graphene using molecular beam experiments and molecular dynamics

Cited by 10 publications

References 13 publications

Scattering Dynamics of Glycine, H2O, and CO2 on Highly Oriented Pyrolytic Graphite

Scattering Dynamics of Glycine, H2O, and CO2 on Highly Oriented Pyrolytic Graphite

Development and validation of a finite-rate model for carbon oxidation by atomic oxygen

Chemical Dynamics Simulation of Low Energy N2 Collisions with Graphite

Contact Info

Product

Resources

About

Scattering Dynamics of Glycine, H₂O, and CO₂ on Highly Oriented Pyrolytic Graphite

Scattering Dynamics of Glycine, H₂O, and CO₂ on Highly Oriented Pyrolytic Graphite

Chemical Dynamics Simulation of Low Energy N₂ Collisions with Graphite