Profiles of the S1 potential energy surface of the Nile Red dye along the rotational coordinate of the amino group are computed using time‐dependent density functional theory (TDDFT) and XMCQDPT2/CASSCF. The calculated profiles exhibit two minima corresponding to a planar locally excited (LE) state and a twisted intramolecular charge transfer (TICT) state. The profiles calculated by time‐dependent density functional theory (TDDFT) depend on the weight of the hartree‐fock (HF) exchange in the functional: at 0% exchange, only the TICT minimum exists, whereas at 50% exchange and more there is only the LE minimum. The profiles obtained by TDDFT at 20–25% HF exchange are in qualitative agreement with that obtained by XMCQDPT2/CASSCF calculations. The energy of the charge transfer state is lowered due to the participation of doubly excited configurations and dynamic correlations, which is implicitly included in the density functionals. The solvent effects on the relative energies of the LE and TICT states and on the barrier height are studied using the polarizable continuum model. The effect of hydrogen bonds is studied for a complex of Nile Red with two water molecules. The solvatochromism of Nile Red fluorescence in aprotic polar solvents is explained by nonspecific solvation, which stabilizes the LE state and causes Nile Red fluorescence solvatochromism; in water and alcohols, it is explained by the formation of hydrogen bonds, which stabilize the TICT state and facilitate the LE‐to‐TICT transition. © 2012 Wiley Periodicals, Inc.

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The ab initio model potential method with the spin-free relativistic scheme by eliminating small components Hamiltonian Molecular density functional calculations in the regular relativistic approximation: Method, application to coinage metal diatomics, hydrides, fluorides and chlorides, and comparison with first-order relativistic calculations Small semiconductor silver and gold sulfide clusters (Ag 2 S) n and (Au 2 S) n , nϭ1,2, are studied by valence ab initio calculations with the inclusion of electron correlation at the second-order perturbation theory ͑MP2͒ and coupled-cluster ͓CCSD and CCSD͑T͔͒ levels. Various relativistic and nonrelativistic pseudopotentials are employed to describe the effects of core electrons. Correlation and relativistic effects are essential in determining the geometry and relative stability of monomer and dimer structures. Relativistic effects result in a notable decrease in the calculated interatomic distances, which is especially significant in the case of gold sulfide structures ͑up to 10%͒. Correlation effects markedly increase the stability of compact structures with an increased number of relatively short M...M contacts ͑M...M distances of about 280-330 pm͒. Excluding the correlation of lower-lying valence orbitals ͑sulfur 3s and silver 4d or gold 5d) results in completely opposite predictions. This fact suggests that the effects of d -d and d-outer valence ͑metal ns and sulfur 3p) electron correlation give rise to attractive short-range interactions of intramolecular van der Waals type, which determine the increased stability of more compact cluster structures. However, large-core pseudopotentials strongly exaggerate this effect in the case of gold and give results rather different from those obtained with more valid and accurate small-core pseudopotentials. It is shown that the reason for this deficiency lies in the nature of pseudopotentials themselves rather than in basis-set shortcomings. The atomization and dissociation energies, equilibrium geometrical parameters, dipole moments, and Mulliken populations are calculated and discussed.

LaAlO 3 is one of the potential candidates to replace SiO 2 as a high permittivity dielectric for future generations of metal-oxide-semiconductor field effect transistors. Using first-principles plane-wave calculations within density functional theory, its bulk and surface electronic properties and the relative stability of cubic c-LaAlO 3 ͑001͒ /Si͑001͒ interfaces are investigated. In agreement with experiment, our study shows that the dielectric constant of crystalline LaAlO 3 ͑ϳ30͒ is comparable to that of hexagonal La 2 O 3. To accurately calculate the c-LaAlO 3 ͑001͒ surface energy, several ways of eliminating the surface dipole moment of the polar surface are presented, with the transfer of an oxygen anion from one boundary surface to the other being identified as the energetically most favorable mechanism. We have found that lanthanum-terminated c-LaAlO 3 ͑001͒ /Si͑001͒ interfaces are in general more stable than aluminum-terminated interfaces for both the oxidized and nonoxidized Si͑001͒ surfaces. We have also identified a significant reduction of the c-LaAlO 3 ͑001͒ /Si͑001͒ valence band offset due to the creation of interface dipoles for O-rich interfaces. Analysis of the density of interface states shows that La-Si bonds at the c-LaAlO 3 ͑001͒ /Si͑001͒ interface do not create interface states in the silicon band gap, in contrast to Hf-Si bonds in m-HfO 2 ͑001͒ /Si͑001͒ interfaces studied previously.