Imaging covalent bond formation by H atom scattering from graphene

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Science  26 Apr 2019:
Vol. 364, Issue 6438, pp. 379-382
DOI: 10.1126/science.aaw6378
  • Fig. 1 Rehybridization in the formation of a C–H bond in collisions of an H atom at a graphene surface.

    HZ and CZ are the distances of the H and C atoms from the graphene plane. Three trajectories are shown for H atoms with 1.92 eV incidence energy.

  • Fig. 2

    Bimodal scattering distributions arising from H collisions with graphene. (A to C) Measured H atom scattering energy, ES, and angular, ϑS, distributions with EI = 1.92 eV. Results for three incidence angles, ϑI, are shown. Thus, the normal component of incidence energy, En, varies from 0.5 to 1.4 eV. ϑS = 0 indicates the surface normal direction. Red ticks indicate the specular scattering angles. All observed scattering occurs within 2.8° of the plane defined by incident H atom beam and the surface normal. (D to F) Corresponding simulated scattering distributions, each shifted by ~10° in incidence angles. This shift is discussed in the supplementary materials, materials and methods S5. Each distribution is multiplied by the indicated red number to use the same color bar. Each image represents 1 million trajectories. (G) Analysis of theoretically calculated trajectories for EI = 1.92 eV and ϑI = 35°. Single-bounce trajectories are shown as red and black. Those in black do not cross the barrier to chemical bond formation. A small number of multibounce collisions (blue) are also seen. The simulations include a modeled treatment of the graphene interactions with Pt (supplementary materials, materials and methods S2).

  • Fig. 3 H atom sticking probabilities at graphene.

    Experimentally derived (blue) and theoretically predicted (black) sticking probabilities for EI = 0.99 eV plotted against the normal component of the incidence energy (En). Theoretically predicted sticking probabilities for EI = 1.92 eV are shown in red. Theoretical simulations used a full dimensional EMFT-REBO PES that includes the influence of the Pt substrate with classical molecular dynamics (solid symbols) or ring polymer molecular dynamics (open symbols).

  • Fig. 4 The dynamical mechanism of energy transfer.

    (A) The collision time correlation with H atom energy loss for trajectories that cross the barrier. The collision time is defined as the time spent with a C–H bond distance less than 1.4 Å. (B, C, and D) An average over 60 trajectories that collide on top of a C and pass over the barrier. A collision is labeled “on top” if at the point of closest approach, one C–H distance is smaller than 1.15 Å and three and only three C–H distances are between 1.6 and 2 Å. t = 0 is taken as the time of the H atom’s closest approach. The incidence conditions are identical to those of Fig. 2G. The yellow curve in (B) shows the H distance to surface, HZ; single-bounce collisions dominate. Also shown are the kinetic energy change of H atom (ΔKH, blue), the kinetic energy change of all C atoms (ΔKslab, purple), the kinetic energy of the C atom hit by the H atom (ΔKC, green), and the graphene deformation energy (ΔUdeform, gold). (C) and (D) show the kinetic energy appearing in different C shells. (E) The shell structure.

Supplementary Materials

  • Imaging covalent bond formation by H atom scattering from graphene

    Hongyan Jiang, Marvin Kammler, Feizhi Ding, Yvonne Dorenkamp, Frederick R. Manby, Alec. M. Wodtke, Thomas F. Miller III, Alexander Kandratsenka, Oliver Bünermann

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

    Download Supplement
    • Materials and Methods
    • Figs. S1 to S20
    • Tables S1 and S2
    • References

    Images, Video, and Other Media

    Movie S1
    Animation of H impinging on graphene. The deep binding well develops only after the H atom has reached its point of closest approach.

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