Research ArticleAPPLIED PHYSICS

Prediction of a low-temperature N2 dissociation catalyst exploiting near-IR–to–visible light nanoplasmonics

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Science Advances  22 Dec 2017:
Vol. 3, no. 12, eaao4710
DOI: 10.1126/sciadv.aao4710
  • Fig. 1 N2 dissociation trajectory and energetics on Mo-doped Au(111) surface.

    (A) Periodic slab DFT–predicted stationary and transition-state structures along the MEP for N2 dissociation (only the Au9Mo slab fragments are shown for clarity). (B) Corresponding spin-relaxed ground-state reaction energy curve. The upper red curve in (B) shows evolution of the net spin moment of the system (in μB). (C) Comparison of the DFT effective barrier for N2 dissociation over Mo-doped Au(111) versus over some other metallic surfaces investigated in the literature, plotted against the dissociative adsorption energy [Ru, Cu, Ag, Au, and others (39); Mo and Fe (27); Au-Fe (26)]. (D) Periodic slab DFT spin–constrained energetics, with Sz = 0 and 1. The upper red curve shows the energy splitting between the two spin structures. (E) Same type of curves in (D) for S = 0 and 1 obtained from emb-NEVPT2 (n-electron valence second-order perturbation theory). (F) emb-NEVPT2–predicted ground- and excited-state energy curves for S = 0, showing up to the sixth excited state. Possible lower-barrier trajectories are marked with arrows. Ground- and excited-state effective thermal barriers are shown on the right margin (in eV and kJ/mol).

  • Fig. 2 CAS natural orbitals from CASSCF.

    (A) Ground-state CASSCF natural orbitals demonstrating qualitative changes in the Mo-N2 bonding interactions in select structures along the dissociation trajectory (see orbital occupations in table S4). Orbitals above the black horizontal dashed line are nearly empty (virtual), and below are nearly completely filled (occupied). Arrows mark orbital lineage. Thick dashed arrows between s:10 and s:13 and s:13 and s:16 indicate crossing of an occupied orbital character (N2 π) into the virtual space or of a virtual (N2 π*) into the occupied space. Isosurface value: 0.02 atomic units (au); the Au10Mo-embedded cluster model + N2 are shown (see Fig. 1A for structural legend). (B) Schematic representation of the bonding orbital interactions between Mo 4d and N2 π or π* in s:6, s:13, and s:16.

  • Fig. 3 Oscillator strengths and electron density differences.

    (Top) Absorption spectrum (oscillator strength, f, versus excitation energy) for select structures along the dissociation trajectory (Fig. 1F), calculated from emb-SA-CASSCF transition dipole moments and emb-NEVPT2 excitation energies. Excited-state index given at the top of each red vertical line. Note that vertical scale changes across the panels. (Bottom) Real-space electron density difference plots between the fifth excited state and the ground state for s:0, s:6, s:10, s:12, and s:13 from emb-SA-CASSCF. Red is electron loss, blue is electron gain, and isosurface value is ±0.002 au; the Au10Mo-embedded cluster model + N2 are shown (see Fig. 1A for structural legend).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/12/eaao4710/DC1

    Supplementary Text

    fig. S1. Mechanisms of chemical enhancement on an MNP via an LSPR.

    fig. S2. Adsorbate vibrational spectra.

    fig. S3. Structural parameters versus reaction coordinate.

    fig. S4. Metal cluster and embedding potential.

    fig. S5. Reaction energy curve using a smaller basis set.

    fig. S6. Singlet-triplet energy as a function of embedded metal cluster CAS size.

    fig. S7. Additional CASSCF natural orbitals.

    fig. S8. N2 charge versus reaction coordinate.

    fig. S9. Comparison of the ground-state energy curves predicted by SA-CASSCF and SS-CASSCF.

    fig. S10. Additional SA-CASSCF(12e,12o) electron difference density plots.

    table S1. GTO basis sets.

    table S2. Benchmark values for the gas-phase N2 dissociation energy (eV) with respect to the method and basis set used.

    table S3. Dependence of reaction energies on basis set.

    table S4. Ground-state CAS natural orbital occupations.

    table S5. Dependence of reaction energies on CAS size.

    movie S1. DFT + D3 CI-NEB–predicted structures along pathway a (physical adsorption).

    movie S2. DFT + D3 CI-NEB–predicted structures along pathway b (reorientation).

    movie S3. DFT + D3 CI-NEB–predicted structures along pathway c (dissociation).

    data file S1. Atomic structure files.

    References (7376)

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Text
    • fig. S1. Mechanisms of chemical enhancement on an MNP via an LSPR.
    • fig. S2. Adsorbate vibrational spectra.
    • fig. S3. Structural parameters versus reaction coordinate.
    • fig. S4. Metal cluster and embedding potential.
    • fig. S5. Reaction energy curve using a smaller basis set.
    • fig. S6. Singlet-triplet energy as a function of embedded metal cluster CAS size.
    • fig. S7. Additional CASSCF natural orbitals.
    • fig. S8. N2 charge versus reaction coordinate.
    • fig. S9. Comparison of the ground-state energy curves predicted by SA-CASSCF and SS-CASSCF.
    • fig. S10. Additional SA-CASSCF(12e,12o) electron difference density plots.
    • table S1. GTO basis sets.
    • table S2. Benchmark values for the gas-phase N2 dissociation energy (eV) with respect to the method and basis set used.
    • table S3. Dependence of reaction energies on basis set.
    • table S4. Ground-state CAS natural orbital occupations.
    • table S5. Dependence of reaction energies on CAS size.
    • Legends for movies S1 to S3
    • Legend for data file S1
    • References (73–76)

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    Other Supplementary Material for this manuscript includes the following:

    • movie S1 (.mp4 format). DFT + D3 CI-NEB–predicted structures along pathway a (physical adsorption).
    • movie S2 (.mp4 format). DFT + D3 CI-NEB–predicted structures along pathway b (reorientation).
    • movie S3 (.mp4 format). DFT + D3 CI-NEB–predicted structures along pathway c (dissociation).
    • data file S1. Atomic structure files.

    Files in this Data Supplement:

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