Zimmermannhermann0163

The electronic and charge transport properties of porphyrin and tetra-indole porphyrinoid single layer covalent organic frameworks (COFs) are investigated by means of density functional theory calculations. Ultrathin diacetylene-linked COFs based on oxidized tetra-indole cores are narrow gap 2D semiconductors, featuring a pronounced anisotropic electronic band structure due to the combination of dispersive and flat band characteristics, while registering high room temperature charge carrier mobilities. The capability of bandgap and charge carrier localization tuning via the careful selection of fourfold porphyrin and porphyrinoid cores and twofold articulated linkers is demonstrated, with the majority of systems exhibiting electronic gap values between 1.75 eV and 2.3 eV. Tetra-indoles are also capable of forming stable monolayers via non-articulated core fusing, resulting in 2D morphologies with extended π-conjugation and semi-metallic behavior.Analytic energy gradients with respect to nuclear motion are derived for non-singlet compounds in the natural orbital functional theory. We exploit the formulation for multiplets in order to obtain a simple formula valid for any many-electron system in its ground mixed state with a total spin S and all possible spin projection Sz values. #link# We demonstrate that the analytic gradients can be obtained without resorting to linear response theory or involving iterative procedures. A single evaluation is required, so integral derivatives can be computed on-the-fly along the calculation, thus improving the effectiveness of screening by the Schwarz inequality. The results for small- and medium-sized molecules with many spin multiplicities are shown. Our results are compared with the experimental data and accurate theoretical equilibrium geometries.For the first time, equations are derived for computing stationary vibrational states with extended vibrational coupled cluster (EVCC) and for propagating nuclear wave packets using time-dependent EVCC (TDEVCC). Expressions for energies, properties, and auto-correlation functions are given. For TDEVCC, convergence toward the ground state for imaginary-time propagation is shown, as well as separability in the case of non-interacting subsystems. The analysis focuses substantially on the difference between bra and ket parameterizations for EVCC and TDEVCC compared to normal vibrational coupled cluster (VCC) and time-dependent VCC (TDVCC). A pilot implementation is presented within a new full-space framework that offers easy access to completely general, albeit not efficient, implementations of alternative VCC variants, such as EVCC. The new methods were tested on 35 three- and six-mode molecular systems. Both EVCC[k] and TDEVCC[k] showed good, hierarchical convergence toward the exact limit. This convergence was generally better than for normal VCC[k] and TDVCC[k] and better still than for (time-dependent) vibrational configuration interaction, though this should be balanced with the higher computational complexity of EVCC. The results highlight the importance of exponential parameterizations and separability in general, as seen, in particular, for the TDEVCC bra parameterization, which is in contrast to the partially linear one of TDVCC. With the results being rooted in the general structures of coupled cluster (CC) theory, they are expected to be relevant to other applications of both normal and extended CC theory as well.Photochemical electron transfer between freely diffusing molecules has been studied extensively. Here, we try to elucidate how much these works have contributed to the understanding of electron transfer. To this end, we have revisited the work performed in the experimental and theoretical areas of concern from the beginning of the 20th century up to the present day. We present a critical look at the major contributions and compile the current picture of a variety of phenomena around electron transfer in solution. This is based on two main developments, besides the theory of Marcus encounter theories of diffusion and laser techniques in time-resolved spectroscopy.Provided in this paper is a theory of long-range electron transfer with near sound (supersonic or subsonic) velocity along one-dimensional crystal lattices. The theory represents the development of an earlier work by introducing Marcus formulation. To illustrate its application to a realistic case, the theory is used to offer an explanation of two puzzling observations made by Donovan and Wilson in transient photoconduction experiments with non-dopable perfectly crystalline polydiacetylene crystals in the presence of an electric field transport velocity value close to sound velocity being independent of field for four orders of magnitude of field (102 V/m-106 V/m) and, in the low field values, an ultra-high mobility greater than 20 m2/V s. We also study factors eventually leading to lowering of the transport velocity.The low melting point of room temperature ionic liquids is usually explained in terms of the presence of bulky, low-symmetry, and flexible ions, with the first two factors related to the lattice energy while an entropic effect is attributed to the latter. By means of molecular dynamics simulations, the melting points of 1-ethyl-3-methyl-imidazolium hexafluorophosphate and 1-decyl-3-methyl-imidazolium hexafluorophosphate were determined, and the effect of the molecular flexibility over the melting point was explicitly computed by restraining the rotation of dihedral angles in both the solid and the liquid phases. The rotational flexibility over the bond between the ring and the alkyl chain affects the relative ordering of the anions around the cations and results in substantial effects over both the enthalpy and the entropy of melting. For the other dihedral angles of the alkyl group, the contributions are predominantly entropic and an alternating behavior was found. The flexibility of some dihedral angles has negligible effects on the melting point, while others can lead to differences in the melting point as large as 20 K. This alternating behavior is rationalized by the different probabilities of conformation defects in the crystal.We explore the use of the stochastic resolution-of-the-identity (sRI) with the phaseless auxiliary-field quantum Monte Carlo (ph-AFQMC) method. sRI is combined with four existing local energy evaluation strategies in ph-AFQMC, namely, (1) the half-rotated electron repulsion integral tensor (HR), (2) Cholesky decomposition (CD), (3) tensor hypercontraction (THC), or (4) low-rank factorization (LR). We demonstrate that HR-sRI achieves no scaling reduction, CD-sRI scales as O(N3), and THC-sRI and LR-sRI scale as O(N2), albeit with a potentially large prefactor. Furthermore, the walker-specific extra memory requirement in CD is reduced from O(N3) to O(N2) with sRI, while sRI-based THC and LR algorithms lead to a reduction from O(N2) extra memory to O(N). Based on numerical results for one-dimensional hydrogen chains and water clusters, we demonstrated that, along with the use of a variance reduction technique, CD-sRI achieves cubic-scaling without overhead. link2 In particular, we find that for the systems studied, the observed scaling of standard CD is O(N3-4), while for CD-sRI, it is reduced to O(N2-3). Once a memory bottleneck is reached, we expect THC-sRI and LR-sRI to be preferred methods due to their quadratic-scaling memory requirements and their quadratic-scaling of the local energy evaluation (with a potentially large prefactor). The theoretical framework developed here should facilitate large-scale ph-AFQMC applications that were previously difficult or impossible to carry out with standard computational resources.Ambient pressure XPS has demonstrated its great potential in probing the solid/liquid interface, which is a central piece in electrocatalytic, corrosion, and energy storage systems. Despite the advantage of ambient pressure XPS being a surface sensitive characterization technique, the ability of differentiating the surface adsorbed species (∼Å scale) and bulk electrolyte (∼10 nm scale) in the spectrum depends on the delicate balance between bulk solution concentration (C), surface coverage (θ), bulk liquid layer thickness (L), and inelastic mean free path (λ) as a function of photon energy. By investigating a model system of gold dissolving in a bromide solution, the connection between theoretical prediction at the atomic resolution and macroscopic observable spectrum is established.We investigate the role of excitonic coupling between retinal chromophores of Krokinobacter eikastus rhodopsin 2 (KR2) in the circular dichroism (CD) spectrum using an exciton model combined with the transition density fragment interaction (TDFI) method. Although the multimer formation of retinal protein commonly induces biphasic negative and positive CD bands, the KR2 pentamer shows only a single positive CD band. The TDFI calculation reveals the dominant contribution of the Coulomb interaction and negligible contributions of exchange and charge-transfer interactions to the excitonic coupling energy. The exciton model with TDFI successfully reproduces the main features of the experimental absorption and CD spectra of KR2, which allow us to investigate the mechanism of the CD spectral shape observed in the KR2 pentamer. The results clearly show that the red shift of the CD band is attributed to the excitonic coupling between retinal chromophores. Further analysis reveals that the weak excitonic coupling plays a crucial role in the shape of the CD spectrum. link3 The present approach provides a basis for understanding the origin of the KR2 CD spectrum and is useful for analyzing the mechanism of chromophore-chromophore interactions in biological systems.Kinetics of photoinduced intramolecular charge separation (CS) and the ensuing ultrafast charge recombination (CR) in electron-donor-acceptor dyads are studied numerically, taking into account the excitation of charge-transfer active intramolecular vibrations and multiple relaxation time scales of the surrounding polar solvent. Both energetic and dynamic properties of intramolecular and solvent reorganization are considered, and their influence on the CS/CR kinetics and quantum yield of ultrafast CS is explored. Particular attention is paid to the energy efficiency of CS, as one of the most important parameters indicating the promise of using a molecular compound as a basis for emerging optoelectronic devices. The CS quantum yield and the energy efficiency of CS are shown to depend differently on the key model parameters. Necessary conditions for the highly efficient CS are evaluated using analytic formulae for the electron transfer rates and derived from numerical simulation data. The reasons why low-exergonic CS taking place in the Marcus normal region can be much slower than CR in the deep inverted region are discussed.In this paper, the fifth of our series focused on the dielectric spectrum symmetrical broadening of water, we consider the solutions of methemoglobin (MetHb) in pure water and in phosphate-buffered saline (PBS). The universal character of the Cole-Cole dielectric response, which reflects the interaction of water dipoles with solute molecules, was described in Paper I [E. Levy et al., J. Chem. Phys. 136, 114502 (2012)]. ML 210 enables the interpretation of the dielectric data of MetHb solutions in a unified manner using the previously developed 3D trajectory method driven by the protein concentration. It was shown that protein hydration is determined by the interaction of water dipoles with the charges and dipoles located on the rough surfaces of the protein macromolecules. In the case of the buffered solution, the transition from a dipole-charged to a dipole-dipole interaction with the protein concentration is observed see Paper III [A. Puzenko et al., J. Chem. Phys. 137, 194502 (2012)]. A new approach is proposed for evaluating the amount of hydration water molecules bounded to the macromolecule that takes into account the number of positive and negative charges on the protein's surface.