Laser-Controlled Dissociation of C2H22+: Ehrenfest Dynamics Using Time-Dependent Density Functional Theory

Effects of Nanowire Doping on Plasmon-Enhanced N2 Dissociation

Doping a transition metal element into plasmonic systems can tune the optical properties of the system, which will potentially facilitate the plasmon-enhanced catalytic process. In this study, we applied the linear-response time-dependent density functional theory (LR-TDDFT) method with real-time electron dynamics and mean-field Ehrenfest dynamics methods to computationally investigate the effects of doping silver nanowires on plasmon-enhanced N2 dissociation. We calculated the absorption spectra for different doped systems, applied an external electric field to the system, and performed mean-field Ehrenfest dynamics to examine how plasmonic excitation will affect the N2 activation or dissociation. In addition, we also studied how the transition metal dopant affects the system's electronic structure and potential energy surface.

First Principles Dynamics Study of Excited Hole Relaxation in DNA

A recent theoretical work showed that ion irradiation generates excited holes deep within the valence band of DNA. In this work, we investigate the excited hole relaxation toward HOMO using a first-principles computational method following such ionization events. The excited hole relaxation is found to depend significantly on the energetic position of the excited hole generated. The relaxation process is found to be an order of magnitude slower for holes that are generated deeper than 20 eV than those generated within 10 eV, where the probability for the initial ionization events is the highest. However, the excited holes that are generated in different spatial moieties such as DNA nucleotide bases and phosphate backbones do not show noticeable differences in terms of the relaxation time. Our work also shows that decoherence due to nuclei dynamics slows down the relaxation by a factor of two or more. At the same time, the relaxation time is found to be less than a couple of picoseconds, much shorter than typical timescales associated with chemical bond dissociation.

Ultrafast Coherent Electron-Hole Separation Dynamics in a Fullerene Derivative

The use of fullerene derivatives as electron donors in bulk heterojunctions is a promising development in the search for efficient energy conversion in hybrid solar cells. A long-lived photoexcited electron-hole pair will give rise to increased efficiency in photoenergy conversion. One way to prevent fast electron-hole recombination is to engineer fullerene derivatives that exhibit intrinsic electron-hole separation through accessible charge-transfer excited states. In this letter, the dynamics of photoexcited electron-hole pairs in a C60 derivative is studied using the real-time time-dependent density functional theory. Although the charge-transfer excited state is not directly accessible from the ground state, intrinsic coherent electron-hole separation is observed following photoexcition as a result of direct coupling between excited states. Ultrafast charge-transfer dynamics is the dominant phenomenon in <60 fs after visible photoexcitation. This work provides insights into the characteristics of ultrafast dynamics in photoexcited fullerene derivatives, and aids in the rational design of efficient solar cells.