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Electron transport in nanostructures is calculated and compared using a time-independent and a time-dependent first-principles framework. The time-independent approach uses the nonequilibrium Green's-function technique to calculate the current, while the time-dependent method extracts the current from the time propagated wave function. The approaches have been tested using gold-benzene-dithiolate-gold and gold-bipyridine-gold molecular junctions. The reasons for the differences in the current-voltage curves predicted by the two methods are discussed. [ABSTRACT FROM AUTHOR]

A multidomain decomposition method is presented for time-dependent density functional calculations. The multidomain decomposition approach divides the coordinate space into subdomains where local solutions are generated. The subdomain solutions are used as basis states to describe the time propagation of electronic wave functions in the whole system. The applicability and flexibility of the approach are demonstrated on various test systems including the calculation of the photoabsorption cross section of a graphene ribbon and a light-harvesting triad. [ABSTRACT FROM AUTHOR]

In the framework of real-time real-space time-dependent density functional theory complemented with Ehrenfest molecular dynamics we have studied the response of small graphene and graphane fragments to intense femtosecond laser pulses. In particular, we have investigated how the response changes with laser pulses of different frequency (near IR, visible, and UV). The results of our simulations show that graphene has a very high immediate (i.e., within laser-pulse duration) damage threshold. They also suggest that, similar to the case of other hydrogenated surfaces, it should be possible to selectively desorb hydrogens from graphane without destroying the underlying carbon structure provided that the laser pulse parameters are properly chosen. [ABSTRACT FROM AUTHOR]

Time-dependent density functional theory simulation of laser-induced ionization is presented. Various test systems including a small wire-like molecule, C12H14, as well as carbon nanotubes with varying diameter are studied. It has been demonstrated that significant ionization electron current is produced when a laser pulse is applied. Moreover, pulse-like patterns of the current have been observed, which suggests that short laser pulses can be used to create spatially and temporally localized electron sources. [ABSTRACT FROM AUTHOR]

A method to calculate the transmission coefficient in multiterminal systems is presented. By adding a complex absorbing potential to the Hamiltonian of the semi-infinite leads, the problem of inverting an infinite dimensional matrix is transformed into a finite dimensional eigenvalue problem. Using this approach transmission coefficients are calculated for all energies at once. The accuracy of the approach is demonstrated with an analytically solvable model system. Numerical examples of a four-terminal graphene cross junction and six-terminal carbon nanotube junction are presented. [ABSTRACT FROM AUTHOR]

The collision of energetic ions and graphene fragments is studied in the framework of real-space finite-difference time-dependent density functional theory (TDDFT) coupled with classical molecular dynamics for nuclei. The amount of energy transferred from the projectile to the target is calculated to explore the defect formation mechanisms as a function of the projectile's energy. It is found that creation of defects in graphene due to the interaction of a fast proton with valence electrons is unlikely. In the case of projectiles with higher charges, the transferred energy increases significantly, leading to higher probability of bond breaking. [ABSTRACT FROM AUTHOR]