The role of a radial ion-track distribution in semiconductors studied by numerical simulations

The effect of radial ion-track distribution on the transient current in semiconductors caused by a high-energy heavy ion strike was studied. Reasonable agreement was observed in experimental and calculated transient currents for ion energies ranging from several to several hundred MeV when the radius of the ion track used in the numerical simulations was shorter or equivalent to that of the penumbra radius.     

On Koopmans' theorem in density functional theory

This paper clarifies why long-range corrected (LC) density functional theory gives orbital energies quantitatively. First, the highest occupied molecular orbital and the lowest unoccupied molecular orbital energies of typical molecules are compared with the minus vertical ionization potentials (IPs) and electron affinities (EAs), respectively. Consequently, only LC exchange functionals are found to give the orbital energies close to the minus IPs and EAs, while other functionals considerably underestimate them. The reproducibility of orbital energies is hardly affected by the difference in the short-range part of LC functionals. Fractional occupation calculations are then carried out to clarify the reason for the accurate orbital energies of LC functionals. As a result, only LC functionals are found to keep the orbital energies almost constant for fractional occupied orbitals. The direct orbital energy dependence on the fractional occupation is expressed by the exchange self-interaction (SI) energy through the potential derivative of the exchange functional plus the Coulomb SI energy. On the basis of this, the exchange SI energies through the potential derivatives are compared with the minus Coulomb SI energy. Consequently, these are revealed to be cancelled out only by LC functionals except for H, He, and Ne atoms.     

Formation mechanism of element distribution in glass under femtosecond laser irradiation

We report on the formation mechanism of element distribution in glass under high-repetition-rate femtosecond laser irradiation. We simultaneously focused two beams of femtosecond laser pulses inside a glass and confirmed the formation of characteristically shaped element distributions. The results of the numerical simulation in which we considered concentration- and temperature-gradient-driven diffusions were in excellent qualitative agreement with the experimental results, indicating that the main driving force is the sharp temperature gradient. Since the composition of a glass affects its refractive index, absorption, and luminescence property, the results in this study provide a framework to fabricate a functional optical device such as optical circuits with a high-repetition-rate femtosecond laser.     

Palladium‐Catalyzed Asymmetric Reductive Heck Reaction of Aryl Halides

Asymmetric reductive Heck reaction of aryl halides is realized in high stereoselectivity. Hydrogen‐bond donors, trialkylammonium salts in a glycol solvent, were used to promote halide dissociation from neutral arylpalladium complexes to access cationic, stereoselective pathways.