Elucidate gmbh4/5/2023 ![]() ![]() The applied electric field had a width of approximately 50 fs, a frequency of 2.5 eV, and a maximum field strength ranging from 0.05 to 0.1 Ry bohr –1 e –1 (from 1.29 to 2.57 V/Å). (16) RT-TD-DFT has also been used to study reaction-induced excitations in nanoparticles. (14,15) In addition, Ag nanowires and N 2 were studied using RT-TD-DFT with Ehrenfest dynamics where it was suggested that charge transfer between Ag σ orbitals and N 2 antibonding orbitals drove N 2 dissociation. These studies suggested that H 2 dissociation was driven by the transfer of charge to the antibonding σ* orbital of the adsorbate. ![]() (10−13) Some work has been performed using linear response TD-DFT and RT-TD-DFT to study light-driven dissociation of H 2 on Au nanoparticles. (9) Several studies have investigated icosahedral Ag and Au nanoparticles to probe the nature of the plasmon resonance as a function of nanoparticle size. RT-TD-DFT has been used to study plasmon generation in Ag 55 nanoclusters, where it was found that d states were important for hot-carrier generation and that hot-carrier generation could be enhanced if the d-to-s excitations were resonant with the plasmon frequency. Real-time, time-dependent density functional theory (RT-TD-DFT) allows for the evaluation of excited state dynamics that cannot be simulated with ground state DFT. One way to gain atomic-scale insight into the mechanism is via a real-time dynamic approach. ![]() ![]() (6−8)ĭisentangling the contribution of each of these proposed mechanisms is difficult using experiments or traditional calculation methods. For example, in previous experimental work on O 2 dissociation on Ag, both the hot electron transfer mechanism and the direct interaction between O 2 molecules with surface plasmon near fields have been proposed in different systems. (6) Previous studies have proposed that one or more of these mechanisms are important, but direct electronic-level insight is difficult to obtain. An additional possibility is local heating, in which heat produced by the decay of the LSP generates a vibrational excitation. This amplified field could be large enough to promote direct intramolecular excitation and dissociate an adsorbate close to the metal surface without the need for charge transfer between the metal and adsorbate. (6) Alternatively, instead of charge transfer, the mechanism could involve the enhancement or amplification of the applied electric field near the metal surface. A related but distinct mechanism involves direct excitation between the metal and adsorbate states. These hot electrons could then transfer to unoccupied orbitals of surface intermediates to break chemical bonds and accelerate reactions. One potential mechanism of action involves the decay of the LSP into so-called “hot” electrons. (1,5) There are a number of mechanisms by which the LSP could interact with adsorbates to promote reaction. Plasmon-mediated reactions are induced via a localized surface plasmon (LSP), which refers to a strong oscillation in a metal’s free electron density. Additionally, charge density and density of states calculations indicate that these excitations are π → π* on short time scales and a mixture of π, σ → π*, σ* over time. Our results also demonstrate that the electric-field enhancement is the primary driving factor for the plasmon-driven dissociation of O 2 on Au and Ag nanoparticles, while for N 2 dissociation, both charge transfer and field enhancement appear to play important roles. We find that RT-TD-DFT with Ehrenfest dynamics gives results that are consistent with experimental tests of plasmonic excitations, in that the presence of nanoparticles facilitates light-induced molecular dissociation. Here, we utilize real-time, time-dependent density functional theory (RT-TD-DFT) to excite systems with oscillating electric fields and track the subsequent excited state dynamics in real time. Understanding the precise workings of plasmon-driven reactions is crucial for the rational design of novel catalytic structures. While plasmonic photocatalysis is a well-known phenomenon, the exact mechanism of these reactions is still debated. Plasmonic metal nanoparticles offer an interesting alternative to traditional heterogeneous catalytic processes due to their ability to harness energy from light. ![]()
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