[en] Time-dependent density functional theory (TDDFT) is based on a set of ideas and theorems quite distinct from those governing ground-state DFT, but emphasizing similar techniques. Today, the use of TDDFT is rapidly growing in many areas of physics, chemistry and materials sciences where direct solution of the Schroedinger equation is too demanding. This is the first comprehensive, textbook-style introduction to the relevant basics and techniques. (orig.)

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[en] We present a generalization of the electron localization function (ELF) that can be used to analyze time-dependent processes. The time-dependent ELF allows the time-resolved observation of the formation, the modulation, and the breaking of chemical bonds, and can thus provide a visual understanding of complex reactions involving the dynamics of excited electrons. We illustrate the usefulness of the time-dependent ELF by two examples: the π-π* transition induced by a laser field, and the destruction of bonds and formation of lone pairs in a scattering process

[en] Full text: We present some of our most recent applications of a computational scheme based on time-dependent density functional theory (TDDFT) and a real-space, real time, numerical framework, for the simulation of processes involving high-intensity optical and UV laser irradiation of molecules and clusters. We address the question which exchange and correlation functional performs best in this situation. We sketch the possibilities and prospects on how to calculate high-harmonic generation, photoionization as well as processes involving the electron-ion dynamics, such as photodissociation and photoisomerization. (author)

[en] The electronic structure with spin–orbit effects of the yttrium nitride YN molecule are investigated by the methods of multireference single and double configuration interaction, including Davidson correction to account for quadruple excitations (MRSDCI + Q). Spin–orbit effects are taken into account via a semi-empirical pseudo-potential for the yttrium atom, while they have been neglected for nitrogen. The potential energy curves are calculated along with the spectroscopic constants for the lowest lying 38 spin–orbit states Ω in YN. A good agreement is displayed by comparing the calculated spectroscopic constants with those available experimentally. The permanent dipole moments are calculated along with the vibrational energies. We identify two vibrational energy levels in the spectra of the yttrium nitride molecule X¹∑⁺ (v = 0) → (1)¹∑⁺ (v′ = 0) that satisfy the criteria of laser cooling in molecules. New results are obtained in the present work for 32 spin orbit states and their spectroscopic constants calculated

[en] Graphical abstract: For the molecule YS the potential energy curves of 55 electronic states in the representation Ω^(±), including the spin–orbit (SO) effects, have been calculated along with the corresponding spectroscopic constants, the permanent dipole moments, the eigenvalues E_v, the rotational constants B_v, the centrifugal distortion constant D_v and the abscissa of the turning points r_min and r_max. Highlights: ► The potential energy curves of 55 electronic states have been investigated. ► Twenty-one new electronic states have been studied for the first time. ► Up to v = 28, E_v, B_v, D_v, r_min and r_max have been calculated. ► The energy T_e, the constants r_e, ω_e, and B_e are determined. - Abstract: An ab initio calculation (single and double excitation plus Davidson correction) have been performed for the molecule Yttrium monosulfide YS. The potential energy curves of 55 electronic states in the representation Ω^(±), including the spin–orbit (SO) effects, have been calculated along with the corresponding spectroscopic constants. The SO effects are taken into account via a semi-empirical pseudo-potential for yttrium atom, while they have been neglected for sulfur. A very good agreement is displayed by comparing the present results with those obtained experimentally for the two states ²Π_1/2 and ⁴Π_1/2. For the investigated electronic states without spin–orbit, the permanent dipole moments as a function of the internuclear distance, the eigenvalues E_v, the rotational constants B_v, the centrifugal distortion constant D_v and the abscissa of the turning points r_min and r_max have been investigated. New results have been obtained for 21 electronic states including their SO components

[en] How fast can a laser pulse ionize an atom? We address this question by considering pulses that carry a fixed time-integrated energy per-area, and finding those that achieve the double requirement of maximizing the ionization that they induce, while having the shortest duration. We formulate this double objective quantum optimal control problem by making use of the Pareto approach to multi-objective optimization, and the differential evolution genetic algorithm. The goal is to find out how a precise time-profiling of ultra-fast, large-bandwidth pulses may speed up the ionization process. We work on a simple one-dimensional model of hydrogen-like atoms (the Poeschl-Teller potential) that allows to tune the number of bound states that play a role in the ionization dynamics. We show how the detailed shape of the pulse accelerates the ionization, and how the presence or absence of bound states influences the velocity of the process. (authors)

[en] Since the discovery of carbon nanotubes (CNT), transmission electron microscopy (TEM) has been the most important tool in their investigation. It is possible to use electron irradiation in a TEM to construct a single-walled carbon nanotube (SWCNT) from an amorphous carbon film. Here we show that such a synthesis method creates a large number of carbon ad-atoms, which after some critical amount of radiation act to restore the system by reconstructing the carbon film. The behavior of the ad-atoms can be controlled by adjusting the current density in the microscope, suggesting that carbon nanomaterials can be tailored by electron irradiation

[en] The discovery of superconductivity in MgB₂, with a rather high transition temperature, has triggered a large number of theoretical and experimental investigations on important issues such as, e.g., the role of gap anisotropy over the Fermi surface (multi-gap superconductivity). We report here the results obtained in this compound using the density functional theory for superconductors, recently proposed by the authors. Without invoking any adjustable parameters, such as μ *, we obtain the transition temperature, the gaps, and the specific heat in very good agreement with experiment. Moreover, our calculations allow for a detailed study of how the phonon-mediated attraction and Coulomb repulsion act differently on σ and π states, thereby stabilizing the observed superconducting phase