Simple finite field nuclear relaxation method for calculating vibrational contribution to degenerate four-wave mixing

A simple extended finite field nuclear relaxation procedure for calculating vibrational contributions to degenerate four-wave mixing (also known as the intensity-dependent refractive index) is presented. As a by-product one also obtains the static vibrationally averaged linear polarizability, as well as the first and second hyperpolarizability. The methodology is validated by illustrative calculations on the water molecule. Further possible extensions are suggested

Vibration and two-photon absorption

The rigorous and transparent treatment of the effects of nuclear vibrational motion in two-photon absorption (TPA) was discussed. Perturbation formula for diatomic molecules were developed and applied to the X¹Σ+–A¹Π transition in CO. The analysis showed that the vibrations played an important role in TPA, just as their role in the calculation of conventional nonlinear optical (NLO) hyperpolarizabilities

Negative Fukui functions: new insights based on electronegativity equalization

The occurrence of negative values for Fukui functions was studied through the electronegativity equalization method. Using algebraic relations between Fukui functions and different other conceptual DFT quantities on the one hand and the hardness matrix on the other hand, expressions were obtained for Fukui functions for several archetypical small molecules. Based on EEM calculations for large molecular sets, no negative Fukui functions were found

Linear response functions for a vibrational configuration interaction state

Linear response functions are implemented for a vibrational configuration interaction state allowing accurate analytical calculations of pure vibrational contributions to dynamical polarizabilities. Sample calculations are presented for the pure vibrational contributions to the polarizabilities of water and formaldehyde. We discuss the convergence of the results with respect to various details of the vibrational wave function description as well as the potential and property surfaces. We also analyze the frequency dependence of the linear response function and the effect of accounting phenomenologically for the finite lifetime of the excited vibrational states. Finally, we compare the analytical response approach to a sum-over-states approach

Simple finite field method for calculation of static and dynamic vibrational hyperpolarizabilities: curvature contributions

In the static field limit, the vibrational hyperpolarizability consists of two contributions due to: (1) the shift in the equilibrium geometry (known as nuclear relaxation), and (2) the change in the shape of the potential energy surface (known as curvature). Simple finite field methods have previously been developed for evaluating these static field contributions and also for determining the effect of nuclear relaxation on dynamic vibrational hyperpolarizabilities in the infinite frequency approximation. In this paper the finite field approach is extended to include, within the infinite frequency approximation, the effect of curvature on the major dynamic nonlinear optical processes

A new efficient approach to the direct restricted active space self-consistent field method

An implicitly parallel method for integral-block driven restricted active space self-consistent field (RASSCF) algorithms is presented. The approach is based on a model space representation of the RAS active orbitals with an efficient expansion of the model subspaces. The applicability of the method is demonstrated with a RASSCF investigation of the first two excited states of indole

Variational calculation of static and dynamic vibrational nonlinear optical properties

The vibrational configuration interaction method used to obtain static vibrational (hyper)polarizabilities is extended to dynamic nonlinear optical properties in the infinite optical frequency approximation. Illustrative calculations are carried out on H2 O and N H3. The former molecule is weakly anharmonic while the latter contains a strongly anharmonic umbrella mode. The effect on vibrational (hyper)polarizabilities due to various truncations of the potential energy and property surfaces involved in the calculation are examined

Energy partitioning for "fuzzy" atoms

The total energy of molecule in terms of 'fuzzy atoms' presented as sum of one- and two-atomic energy components is described. The divisions of three-dimensional physical space into atomic regions exhibit continuous transition from one to another. The energy components are on chemical energy scale according to proper definitions. The Becke's integration scheme and weight function determines realization of method which permits effective numerical integrations

A new all-round density functional based on spin states and SN2 barriers

We report here a new empirical density functional that is constructed based on the performance of OPBE and PBE for spin states and SN 2 reaction barriers and how these are affected by different regions of the reduced gradient expansion. In a previous study [Swart, Sol̀, and Bickelhaupt, J. Comput. Methods Sci. Eng. 9, 69 (2009)] we already reported how, by switching between OPBE and PBE, one could obtain both the good performance of OPBE for spin states and reaction barriers and that of PBE for weak interactions within one and the same (SSB-sw) functional. Here we fine tuned this functional and include a portion of the KT functional and Grimme's dispersion correction to account for π- π stacking. Our new SSB-D functional is found to be a clear improvement and functions very well for biological applications (hydrogen bonding, π -π stacking, spin-state splittings, accuracy of geometries, reaction barriers)

Are the maximum hardness and minimum polarizability principles always obeyed in nontotally symmetric vibrations?

An overview is given on a study which showed that not only in chemical reactions but also in the favorable case of nontotally symmetric vibrations where the chemical and external potentials keep approximately constant, the generalized maximum hardness principle (GMHP) and generalized minimum polarizability principle (GMPP) may not be obeyed. A method that allows an accurate determination of the nontotally symmetric molecular distortions with more marked GMPP or anti-GMPP character through diagonalization of the polarizability Hessian matrix is introduced

Two complementary molecular energy decomposition schemes: the Mayer and Ziegler-Rauk methods in comparison

In the present paper we discuss and compare two different energy decomposition schemes: Mayer's Hartree-Fock energy decomposition into diatomic and monoatomic contributions [Chem. Phys. Lett. 382, 265 (2003)], and the Ziegler-Rauk dissociation energy decomposition [Inorg. Chem. 18, 1558 (1979)]. The Ziegler-Rauk scheme is based on a separation of a molecule into fragments, while Mayer's scheme can be used in the cases where a fragmentation of the system in clearly separable parts is not possible. In the Mayer scheme, the density of a free atom is deformed to give the one-atom Mulliken density that subsequently interacts to give rise to the diatomic interaction energy. We give a detailed analysis of the diatomic energy contributions in the Mayer scheme and a close look onto the one-atom Mulliken densities. The Mulliken density ρA has a single large maximum around the nuclear position of the atom A, but exhibits slightly negative values in the vicinity of neighboring atoms. The main connecting point between both analysis schemes is the electrostatic energy. Both decomposition schemes utilize the same electrostatic energy expression, but differ in how fragment densities are defined. In the Mayer scheme, the electrostatic component originates from the interaction of the Mulliken densities, while in the Ziegler-Rauk scheme, the undisturbed fragment densities interact. The values of the electrostatic energy resulting from the two schemes differ significantly but typically have the same order of magnitude. Both methods are useful and complementary since Mayer's decomposition focuses on the energy of the finally formed molecule, whereas the Ziegler-Rauk scheme describes the bond formation starting from undeformed fragment densities

Innovación docente en la asignatura de didáctica de la actividad física y del deporte a través de una metodología activa

En el marco del nuevo cambio del modelo de enseñanza y de aprendizaje del Espacio Europeo de Educación Superior, se pretende dar a conocer el proceso de enseñanza y de aprendizaje a través de una metodología activa llevado a cabo en la asignatura de Didáctica de la Actividad Física y del Deporte en los estudios de la Licenciatura de Ciencias de la Actividad Física y del Deporte en la Universidad de Alcalá. Los objetivos que se han perseguido en el desarrollo de esta metodología son los siguientes: facilitar un conocimiento más profundo y duradero mediante un aprendizaje activo, favorecer una participación del alumnado en el proceso evaluador, adquirir determinadas competencias necesarias para el ejercicio profesional, beneficiar un aprendizaje por comprensión frente a un aprendizaje memorístico y establecer una mayor interacción entre profesor-alumno y entre alumno-alumno. Para ello, se ha utilizado una combinación de diferentes estrategias metodológicas que potencian la participación activa y autónoma de los alumnos en su propio proceso de aprendizaje a nivel cognitivo, afectivo y social y donde la profesora ha pretendido ser una mediadora y facilitadora del aprendizaje del alumnado, resolviendo dudas y dando las directrices del camino que debe seguir. Igualmente, en la evaluación también ha participado el alumnado a través de la coevaluación, autoevaluación y heteroevaluación del alumnado. De esta forma, a través de una metodología activa en las clases se ha pretendido fomentar un aprendizaje activo a partir de una orientación del aprendizaje por medio de la propia experiencia: aprender a aprender; de la participación del alumnado en el proceso evaluador, del desarrollo del espíritu crítico y de la creatividad, de una orientación de la educación hacia un ambiente socializante, del fomento de la iniciativa del alumno y de la creación de un clima de investigación. No obstante, la profesora, en un proceso de autoevaluación de su propia enseñanza, ha encontrado una serie de limitaciones o inconvenientes en el uso de este tipo de metodología

La Planificación y la acción docente en educación física desde la perspectiva de la acción situada

Los objetivos del presente estudio son: Revisar las aportaciones teóricas desarrolladas desde la perspectiva de la “acción situada” sobre las relaciones entre las fases preinteractiva e interactiva, en la actividad docente en E.F.; Analizar cuestiones epistemológicas y metodológicas y su incidencia en el desarrollo de la didáctica de la E.F. como campo disciplinar; Reflexionar sobre cuestiones didácticas en el modelo actual de formación del profesorado

Kinball: los deportes alternativos en la formación del/la docente de educación física

Desde hace años, los maestros y profesores de educación física se han basado en gran medida en los deportes colectivos clásicos, como el fútbol, baloncesto, balonmano, voleibol… para desarrollar su labor pedagógica en sus centros educativos. No obstante, en muchas ocasiones sus clases se han convertido en una mera transmisión de gestos técnicos más enfocados al deporte como rendimiento que a la función educativa, que debería primar en las sesiones de educación física. En los tiempos actuales, seguir con este modelo tan erróneo y equivocado sería un atraso y de ahí que sea necesario un cambio en esta manera de entender la educación física. Tanto es así que la sociedad, desde hace ya algún tiempo, ha venido solicitando este cambio exigiendo una mayor calidad del sistema educativo que se debería ver reflejado en un mayor compromiso y cualificación de las personas encargadas de este proceso de enseñanza y aprendizaje

Evaluación evolutiva de la salud percibida según las etapas del cambio del modelo transteórico en el tabaquismo

OBJETIVO: Evaluar la salud percibida en fumadores de cigarrillos según las etapas del cambio. METODOLOGIA: Se estudiaron 253 personas mediante el cuestionario de salud SF-36 cada 6 meses durante dos años. RESULTADOS: Después del abandono del tabaco mejora la Evolución Declarada de la Salud y las percepciones de salud del componente físico y mental. Los fumadores que siguen fumando pero progresan en las etapas del cambio experimentan un descenso en Función Física, Salud General y en el Componente Sumario Físico. La recaída en el tabaquismo se asocia a peor Vitalidad y Salud Mental, y a considerar el consumo de tabaco como causa del deterioro actual de la salud. CONCLUSIONES: Se observa una peor percepción de salud física al plantearse el abandono del consumo de tabaco a medio plazo, una mejoría global de la salud percibida al dejar de fumar y una peor salud emocional en la recaída.