Yosuke Kanai

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Explicit integrators for real-time propagation of time-dependent Kohn-Sham equations are compared regarding their suitability for performing large-scale simulations. Four algorithms are implemented and assessed for both stability and accuracy within a plane-wave pseudopotential framework, employing the adiabatic approximation to the exchange-correlation(More)
A density functional theory approach is employed to investigate poly-3-hexylthiophene (P3HT) interfaced with both a semiconducting and metallic carbon nanotube (CNT). For the semiconducting CNT, a type-II heterojunction can form, making such an interface desirable as a photovoltaic heterojunction. In contrast, with the metallic CNT, substantial charge(More)
A recently proposed approach, called "string method," allows us to find minimum energy pathways connecting two metastable states of a system [W. E et al., Phys. Rev. B 66, 052301 (2002)]. So far this approach has been only used with empirical force field parametrizations of the atomic potential energy surface or in the context of macroscopic continuum(More)
We show that atomistic first-principles calculations based on real-time propagation within time-dependent density functional theory are capable of accurately describing electronic stopping of light projectile atoms in metal hosts over a wide range of projectile velocities. In particular, we employ a plane-wave pseudopotential scheme to solve time-dependent(More)
We have studied the performance of local and semilocal exchange-correlation functionals [meta-generalized-gradient-approximation (GGA)-TPSS, GGA-Perdew-Burke-Ernzerhof (PBE), and local density approximation (LDA)] in the calculation of transition states, reaction energies, and barriers for several molecular and one surface reaction, using the plane-wave(More)
Motivated by recent experiments, we investigate how NO3-SWNT interactions become energetically favorable with varying oxidation state of a single-walled carbon nanotube (SWNT) using first-principles calculations. Chemisorption becomes less endothermic with respect to physisorption when the SWNT oxidation state is elevated. Importantly, the dissociative(More)
In the quest to harness solar energy for power generation, most efforts are centered around photoinduced generic charge separation, such as in photovoltaics, water splitting, other small-molecule activation, and biologically inspired photosynthetic systems. In contrast, the direct collection of heat from sunlight has received much less diversified(More)
Advancement in high-performance computing allows us to calculate properties of increasingly complex materials with unprecedented accuracy. At the same time, to take full advantage of modern leadership-class supercomputers, the calculations need to scale well on hundreds of thousands of processing cores. We demonstrate such high scalability of our recently(More)
The interfacial charge-transfer mechanism of the P3HT/fullerene photovoltaic heterojunction is elucidated using density functional theory calculations. Our findings indicate that an efficient adiabatic electron transfer is highly probable due to the presence of an extended electronic state that has a significant probability distribution across the interface(More)
In this feature article we focus on the key problem of charge separation in nano-scale photovoltaic materials; in particular recent theoretical/computational work based on first principles electronic structure approaches is presented and discussed. We review applications of state-of-the-art electronic structure calculations to nano-scale materials that(More)