Search results for "figuration"
showing 10 items of 615 documents
Configuration Expansion by Means of Pseudonatural Orbitals
1977
The configuration interaction (CI) method as a general approach to solving the many-electron Schrodinger equation to—in principle—any desired accuracy, has been described in this volume by Shavitt. We refer to that chapter for all basic concepts of the CI method and an outline of its merits and its computational problems.
A new approach to interacting fields
1974
A model for a description of interaction, which involves particle creation, can be given as follows: (1) A smooth finite-dimensional manifoldM constitutes the configuration space of some interacting system. (2) The concept of an interacting field is formulated in terms of two-component objects which consist of a physical and a topological field component which are ‘derived’ fromM. (3) Interaction is described in terms of the topological linking number of the topological field components and in terms of the intrinsic field equations.
Spin Transition in Iron Compounds
1984
First-row transition metal complexes with d4 up to d7 electron configuration in octahedral ligand fields (and d8 electron configuration in six-coordinate complexes of lower symmetry) may undergo temperature dependent high spin (HS) ⇌ low spin (LS) transition, provided the ligand field strength (Δ), including low symmetry contributions, becomes comparable in magnitude with the mean spin pairing energy (P). At a critical field strength Δcrit = P, the energy levels of the two spin states cross. This is illustrated in Fig. 1, where a simplified Tanabe-Sugano type energy level diagram for d6 systems (e.g. Fe2+, Co3+) is shown as an example. For weak ligand fields, Δ Δcrit, the LS state1A1g(Oh) b…
The Action Principles in Mechanics
2001
We begin this chapter with the definition of the action functional as time integral over the Lagrangian \(L(q_{i}(t),\dot{q}_{i}(t);t)\) of a dynamical system: $$\displaystyle{ S\left \{[q_{i}(t)];t_{1},t_{2}\right \} =\int _{ t_{1}}^{t_{2} }dt\,L(q_{i}(t),\dot{q}_{i}(t);t)\;. }$$
Electronic States, Absorption Spectrum and Circular Dichroism Spectrum of the Photosynthetic Bacterial LH2 Antenna of Rhodopseudomonas acidophila as …
1999
A new approach that uses a combination of semiempirical configuration interaction method and exciton theory to calculate electronic energies, eigenstates, absorption spectrum and circular dichroism (CD) spectrum of the LH2 antenna of Rhodopseudomonas acidophila is introduced. A statistical simulation that uses experimental homogeneous line widths was used to account for the inhomogeneous line width of the observed spectrum. Including the effect of orbital overlap of the close-lying pigments of the B850 ring and the effect of the pigment protein interaction in the B800 ring allowed a successful simulation of the experimental absorption and CD spectra of the antenna at room temperature. Two e…
Modelling excitonic energy transfer in the photosynthetic unit of purple bacteria
2009
Abstract Molecular mechanics and quantum chemical configuration interaction calculations in combination with exciton theory were used to predict vibronic energies and eigenstates of light harvesting antennae and the reaction centre and to evaluate excitation energy transfer rates in the photosynthetic unit of purple bacteria. Excitation energy transfer rates were calculated by using the transition matrix formalism and exciton basis sets of the interacting antenna systems. Energy transfer rates of 600–800 fs from B800 ring to B850 ring in the LH2 antenna, 3–10 ps from LH2 to LH2 antenna, 2–8 ps from LH2 to LH1 antenna and finally 30–70 ps from LH1 to the reaction centre were obtained. Depend…
Use of Heating Configuration to Control Marangoni Circulation during Droplet Evaporation
2022
The present work presents a numerical study of the evaporation of a sessile liquid droplet deposited on a substrate and subjected to different heating configurations. The physical formulation accounts for evaporation, the Marangoni effect, conductive transfer in the support, radiative heating, and diffusion–convection in the droplet itself. The moving interface is solved using the Arbitrary Lagrangian–Eulerian (ALE) method. Simulations were performed using COMSOL Multiphysics. Different configurations were performed to investigate the effect of the heating conditions on the shape and intensity of the Marangoni circulations. A droplet can be heated by the substrate (different natures and thi…
A wearable multimodal interface for exploring urban points of interest
2015
Locating points of interest (POIs) in cities is typically facilitated by visual aids such as paper maps, brochures, and mobile applications. However, these techniques require visual attention, which ideally should be on the surroundings. Non-visual techniques for navigating towards specific POIs typically lack support for free exploration of the city or more detailed guidance. To overcome these issues, we propose a multimodal, wearable system for alerting the user of nearby recommended POIs. The system, built around a tactile glove, provides audio-tactile cues when a new POI is in the vicinity, and more detailed information and guidance if the user expresses interest in this POI. We evaluat…
Correlation of the Extent of Fjord-Region Oxidation with DNA Binding and Mutagenicity of the Enantiomeric 11,12-Dihydrodiols of Dibenzo[a,l]pyrene
1996
Abstract In vitro studies on the hepatic biotransformation of the enantiomeric trans-11,12-dihydrodiols of dibenzo[a,l]pyrene (DB[a,l]P) using microsomal fractions of animals pretreated with Aroclor 1254 revealed that the formation of fjord-region dihydrodiol epoxides strongly depends on the absolute configuration of the substrate. Both the (-)-11R,12R- and the (+)-11S,12S-enantiomer are converted diastereoselectively to the (-)- and (+)-anti-dihydrodiol epoxide, respectively, by either rat or mouse liver microsomes. Fjord-region oxidation occurs to greatest extent on incubation of the (-)-11R,12R-dihydrodiol with preparations from rats. This finding is in line with the differences seen for…
Computation of conical intersections by using perturbation techniques
2005
Multiconfigurational second-order perturbation theory, both in its single-state multiconfigurational second-order perturbation theory (CASPT2) and multistate (MS-CASPT2) formulations, is used to search for minima on the crossing seams between different potential energy hypersurfaces of electronic states in several molecular systems. The performance of the procedures is tested and discussed, focusing on the problem of the nonorthogonality of the single-state perturbative solutions. In different cases the obtained structures and energy differences are compared with available complete active space self-consistent field and multireference configuration interaction solutions. Calculations on dif…