An official website of the United States government
Routine investigations of plasmonic phenomena at the quantum level present a formidable computational challenge due to the large system sizes and ultrafast timescales involved. This Feature Article highlights the use of density functional tight-binding (DFTB), particularly its real-time time-dependent formulation (RT-TDDFTB), as a tractable approach to study plasmonic nanostructures from a purely quantum mechanical purview. We begin by outlining the theoretical framework and limitations of DFTB, emphasizing its efficiency in modeling systems with thousands of atoms over picosecond timescales. Applications of RT-TDDFTB are then explored in the context of optical absorption, nonlinear harmonic generation, and plasmon-mediated photocatalysis. We demonstrate how DFTB can reconcile classical and quantum descriptions of plasmonic behavior, capturing key phenomena such as size-dependent plasmon shifts and plasmon coupling in nanoparticle assemblies. Finally, we showcase DFTB’s ability to model hot carrier generation and reaction dynamics in plasmon-driven H2 dissociation, underscoring its potential to model photocatalytic processes. Collectively, these studies establish DFTB as a powerful, yet computationally efficient tool to probe the emergent physics of materials at the limits of space and time.
more »
« less
This content will become publicly available on May 8, 2026
Density Functional Tight-Binding Captures Plasmon-Driven H 2 Dissociation on Al Nanocrystals
Aluminum nanocrystals offer a promising platform for plasmonic photocatalysis, yet a detailed understanding of their electron dynamics and consequent photocatalytic performance has been challenging thus far due to computational limitations. Here, we employ density functional tight-binding methods (DFTB) to investigate the optical properties and H2 dissociation dynamics of Al nanocrystals with varying sizes and geometries. Our real-time simulations reveal that Al’s unique free-electron nature enables efficient light-matter interactions and rapid electronic thermalization. Cubic and octahedral nanocrystals ranging from 0.5 to 4.5 nm exhibit size-dependent plasmon resonances in the UV, with distinct spectral features arising from the particle geometry and electronic structure. By simulating H2 dissociation near Al nanocrystals, we demonstrate that hot electrons generated through plasmon excitation can overcome the molecule’s strong chemical bond within tens of femtoseconds. The laser intensity threshold is comparable to previous reports for Ag nanocrystals, though significantly lower than that of Au. Notably, the dipolar plasmon mode demonstrates higher efficiency for this reaction than the localized interband transition for particles at these sizes. Taken together, this work provides mechanistic insights into plasmon-driven catalysis and showcases DFTB’s capability to study quantum plasmonics at unprecedented length and time scales.
more »
« less
- Award ID(s):
- 2347622
- PAR ID:
- 10652517
- Publisher / Repository:
- J. Phys. Chem. C
- Date Published:
- Journal Name:
- The Journal of Physical Chemistry C
- Volume:
- 129
- Issue:
- 18
- ISSN:
- 1932-7447
- Page Range / eLocation ID:
- 8634 to 8644
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
H2 activation is fundamental in catalysis. Single-atom catalysts (SACs) can be highly selective hydrogenation catalysts due to their tunable geometric and electronic properties. In this work, H2 activation (adsorption, splitting, and diffusion) on the anatase TiO2-supported SAC has been modeled in detail. The stable configurations of 14 transition metals from 3d to 5d (Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, Cd, Os, Ir, Pt, and Au) and Sn have been screened. We compared H and H2 adsorption and H2 heterolytic and homolytic splitting on SA/TiO2. H on the SAC in neutral, hydridic, and proton forms and the preferred H2 dissociation paths are revealed. We found that the metal adatoms strengthen the Brønsted acids via forming the SA-O bonds and promote the H adsorption on Ti sites via forming the Ti3+ sites. The electronic descriptor using the energy level of the frontier d orbital, referenced to vacuum, can predict the single H and H2 dissociative adsorption energies on the metal site. As the SA-Hδ- interaction is stronger than Ti-Hδ-, the activation barriers for heterolytic paths over SA-O sites are lower than over Ti-O sites. H2 adsorption is activated on Au, Ru, Rh, Pd, and Ir in a dihydrogen complex structure with an elongated H-H bond. Homolytic splitting over SA sites is favored thermodynamically and kinetically on Rh, Pd, Os, Ir, and Pt. In contrast, for the remaining SA/TiO2, H-H splitting at the SA-O is kinetically favored compared to the Ti-O sites, but the products are less thermodynamically favored.more » « less
-
Abstract Plasmon decay is believed to play an essential role in inducing hot carrier transfer at the interfaces between plasmonic nanoparticles and semiconductor surfaces. In this work, we employ real-time time-dependent density functional theory (RT-TDDFT) simulation in the Wannier gauge to gain quantum-mechanical insights into the nonlinear dynamics of the plasmon decay in the Ag20nanoparticle at a semiconductor surface. The first-principles simulations show that the plasmon decay is more than two times faster when the Ag20nanoparticle is adsorbed on a hydrogen-terminated Si(111) surface, taking place within 100 femtoseconds of the plasmon excitation. Hot carrier transfer across the interface is observed as the plasmon decay takes place, and nearly 30% of holes are generated deep in the valence band of the semiconductor surface. The use of Wannier gauge in RT-TDDFT simulation is particularly convenient for gaining quantum-mechanical insights into non-equilibrium electron dynamics in complex heterogeneous systems.more » « less
-
Research on plasmons of gold nanoparticles has gained broad interest in nanoscience. However, ultrasmall sizes near the metal-to-nonmetal transition regime have not been explored until recently due to major synthetic difficulties. Herein, intriguing electron dynamics in this size regime is observed in atomically precise Au 333 (SR) 79 nanoparticles. Femtosecond transient-absorption spectroscopy reveals an unprecedented relaxation process of 4–5 ps—a fast phonon–phonon relaxation process, together with electron–phonon coupling (∼1 ps) and normal phonon–phonon coupling (>100 ps) processes. Three types of –R capped Au 333 (SR) 79 all exhibit two plasmon-bleaching signals independent of the –R group as well as solvent, indicating plasmon splitting and quantum effect in the ultrasmall core of Au 333 (SR) 79 . This work is expected to stimulate future work on the transition-size regime of nanometals and discovery of behavior of nascent plasmons.more » « less
-
Abstract Ternary metal‐chalcogenide semiconductor nanocrystals are an attractive class of materials due to their tunable optoelectronic properties that result from a wide range of compositional flexibility and structural diversity. Here, the phase‐controlled synthesis of colloidal silver iron sulfide (AgFeS2) nanocrystals is reported and their resonant light–matter interactions are investigated. The product composition can be shifted selectively from tetragonal to orthorhombic by simply adjusting the coordinating ligand concentration, while keeping the other reaction parameters unchanged. The results show that excess ligands impact precursor reactivity, and consequently the nanocrystal growth rate, thus deterministically dictating the resulting crystal structure. Moreover, it is demonstrated that the strong ultraviolet‐visible extinction peak exhibited by AgFeS2nanocrystals is a consequence of a quasi‐static dielectric resonance (DR), analogous to the optical response observed in CuFeS2nanocrystals. Spectroscopic studies and computational calculations confirm that a negative permittivity at ultraviolet/visible frequencies arises due to the electronic structure of these intermediate‐band (IB) semiconductor nanocrystals, resulting in a DR consisting of resonant valence‐band‐to‐intermediate‐band excitations, as opposed to the well‐known localized surface plasmon resonance response typically observed in metallic nanostructures. Overall, these results expand the current library of an underexplored class of IB semiconductors with unique optical properties, and also enrich the understanding of DRs in ternary metal‐iron‐sulfide nanomaterials.more » « less
