Exact Kohn-Sham potential of strongly correlated finite systems

The dissociation of molecules, even the most simple hydrogen molecule, cannot be described accurately within density functional theory because none of the currently available functionals accounts for strong on-site correlation. This problem has led to a discussion of properties that the local Kohn-Sham potential has to satisfy in order to correctly describe strongly correlated systems. We derive an analytic expression for this potential at the dissociation limit and show that the numerical calculations for a one-dimensional two electron model system indeed approach and reach this limit. It is shown that the functional form of the potential is universal, i.e. independent of the details of the system.Comment: 17 pages, 3 figures, submitted to JC

Photo-excitation of a light-harvesting supra-molecular triad: a Time-Dependent DFT study

We present the first time-dependent density-functional theory (TDDFT) calculation on a light harvesting triad carotenoid-diaryl-porphyrin-C60. Besides the numerical challenge that the ab initio study of the electronic structure of such a large system presents, we show that TDDFT is able to provide an accurate description of the excited state properties of the system. In particular we calculate the photo-absorption spectrum of the supra-molecular assembly, and we provide an interpretation of the photo-excitation mechanism in terms of the properties of the component moieties. The spectrum is in good agreement with experimental data, and provides useful insight on the photo-induced charge transfer mechanism which characterizes the system.Comment: Accepted for publication on JPC, March 09th 200

A time-dependent density functional theory scheme for efficient calculations of dynamic (hyper)polarizabilities

We present an efficient perturbative method to obtain both static and dynamic polarizabilities and hyperpolarizabilities of complex electronic systems. This approach is based on the solution of a frequency dependent Sternheimer equation, within the formalism of time-dependent density functional theory, and allows the calculation of the response both in resonance and out of resonance. Furthermore, the excellent scaling with the number of atoms opens the way to the investigation of response properties of very large molecular systems. To demonstrate the capabilities of this method, we implemented it in a real-space (basis-set free) code, and applied it to benchmark molecules, namely CO, H2O, and paranitroaniline (PNA). Our results are in agreement with experimental and previous theoretical studies, and fully validate our approach.Comment: 9 pages, 4 figure

High Excitation Molecular Gas in the Magellanic Clouds

We present the first survey of submillimeter CO 4-3 emission in the Magellanic Clouds. The survey is comprised of 15 6'x6' maps obtained using the AST/RO telescope toward the molecular peaks of the Large and Small Magellanic Clouds. We have used these data to constrain the physical conditions in these objects, in particular their molecular gas density and temperature. We find that there are significant amounts of molecular gas associated with most of these molecular peaks, and that high molecular gas temperatures are pervasive throughout our sample. We discuss whether this may be due to the low metallicities and the associated dearth of gas coolants in the Clouds, and conclude that the present sample is insufficient to assert this effect.Comment: 18 pages, 3 figures, 5 tables. To appear in Ap

Concepciones de contabilidad en estudiantes de la instituci?n educactiva Manuel Murillo Toro jornada diurna grado once tres en la modalidad de administraci?n financiera

102 p. Recurso Electr?nicoEn la actualidad se puede percibir que la mayor?a de estudiantes cultivan sentimientos negativos por el ?rea de las matem?ticas, y todo lo que implica el uso de los n?meros, entre ellas la contabilidad; lo cual impide conocer las diferentes concepciones que tienen los estudiantes sobre la misma lo que a su vez en muchos casos se debe a que tienen un concepto errado de la misma, o no tienen unos fundamentos s?lidos en Matem?ticas dificultando el aprendizaje y todo lo que se derive de ella. Todo esto puede deberse a diferentes factores pedag?gicos, did?cticos, motivacionales, personales, sociales entre otros. Pues en cualquier carrera t?cnica, tecn?loga o universitaria incluye en su pensum acad?mico las Matem?ticas o la Contabilidad; por consiguiente se espera que estos conocimientos le permitan desempe?arse de una forma calculada y mesurada en cuanto a su vida personal, y el manejo de su dinero. Lo anterior llev? al equipo investigativo a plantearse la siguiente pregunta problema: ?Cu?les son las concepciones de la contabilidad en los estudiantes de la Instituci?n Educativa INEM Manuel Murillo Toro, jornada diurna del grado 11-3 de la ciudad de Ibagu? (Tolima)? En vista de lo anterior el presente ejercicio investigativo tuvo como objetivo identificar, analizar, modificar y fortalecer, la concepci?n de Contabilidad en estudiantes de la Instituci?n Educativa INEM Manuel Murillo Toro del grado 11-3. Para lo anterior se us? la Metodolog?a de investigaci?n ? Acci?n, la cual permite intervenir directamente en la situaci?n probl?mica. Como primera medida se seleccion? la instituci?n Educativa, seg?n las modalidades de profundizaci?n se escogi? la instituci?n Inem Manuel Murillo Toro por su modalidad de Contabilidad, en el programa de Administraci?n Financiera en articulaci?n con la Universidad del Tolima y un convenio interinstitucional con la Uniminuto, y en especial se escogi? el grado 11-3 puesto que estos estudiantes desde el grado 9? han escogido esta modalidad y est?n en proceso de culminaci?n de su formaci?n escolar, lo cual permite tener una visi?n general del programa y en particular los conocimientos de la asignatura de Contabilidad. En conclusi?n est? investigaci?n busc? servir como referente y como documento de consulta sobre el ?rea de la Contabilidad, el papel relevante del docente en la formaci?n de esta ?rea, las posibles herramientas a implementar dentro del proceso y su papel decisivo en las concepciones de los estudiantes sobre la Contabilidad. En vista de lo anterior se resalta la importancia de investigar en el aula, partiendo del contexto en que se encuentran inmersos los estudiantes, con el fin de dar respuesta a al desconocimiento de las concepciones que se presentan en el aprendizaje de la Contabilidad y de esta manera contribuir y facilitar el aprendizaje de la mismas de tal forma que estos comprendan la transcendencia de esta ?rea en su cotidianidad.Currently, it can preceived that the majority of students cultivate negative feelings in the area of mathematics, and everything that involves the use of numbers, including accounting. These negavie feelings toward mathematics impede the students from understanding different mathematical concepts or have the wrong idea of the concept or they do not have a strong foundation in Mathematics, and thus it makes it very difficult to learn anything that arises from the mathematical concept. All of this is due to different factors such as: pedagogical, educational, motivational, personal, and social factors among others. In any University, as mathematics is included in the curriculum, technical career or technology. Therefore, this knowlege of mathematics will allow you to enhance your personal life as well, including how you manage money. This, therefore lead the investigative team to ask this problematic question: What accounting concepts do the students from the Inem Manuel Murillo Toro School grade11-3 in the city of Ibague, Tolima have? In view of the above, the present investigative exercise was intended to identify, analyze, modify, y strengthen the conception of accounting for the students in the Educational Institute Inem Manual Murillo Toro from grades 11-3. The technique of research was used for the above action, which allows you to intervene directly in the problematic situation. The first step was selecting the educational institution according to the deepening modalities the Institution of Inem Manuel Murillo Toro was chosen due to its model of accounting, financial management, in coordination with the University of Tolima, and an interinstitutional with Uniminuto, and in special we chose grades 11-3 given that these students have chosen this avenue and are in the process of completing high school, which therefore allows to have a general vision or overview of the program and in particular the accounting.In finding, this investigation sought to serve as a reference and consultation document in the area of accounting, the role of the teacher in the training in this area, and possible tools to be implemented within the process. In view of the above highlights, the importance of research in the classroom, on the basis of the context in which they are immersed students, in order to respond to the various problems which arise in when learning about accounting, and in this way contribute and facilitate the learning of the same so that they understand the significance of this area in their daily lives. Keywords: Accounting, Research-Action, Conceptio

Phonon-driven spin-Floquet magneto-valleytronics in MoS 2

Two-dimensional materials equipped with strong spin-orbit coupling can display novel electronic, spintronic, and topological properties originating from the breaking of time or inversion symmetry. A lot of interest has focused on the valley degrees of freedom that can be used to encode binary information. By performing ab initio time-dependent density functional simulation on MoS 2 , here we show that the spin is not only locked to the valley momenta but strongly coupled to the optical E″ phonon that lifts the lattice mirror symmetry. Once the phonon is pumped so as to break time-reversal symmetry, the resulting Floquet spectra of the phonon-dressed spins carry a net out-of-plane magnetization (≈0.024μ B for single-phonon quantum) even though the original system is non-magnetic. This dichroic magnetic response of the valley states is general for all 2H semiconducting transition-metal dichalcogenides and can be probed and controlled by infrared coherent laser excitation

Dynamical charge inhomogeneity and crystal-field fluctuations for 4f ions in high-Tc cuprates

The main relaxation mechanism of crystal-field excitations in rare-earth ions in cuprates is believed to be provided by the fluctuations of crystalline electric field induced by a dynamic charge inhomogeneity generic for the doped cuprates. We address the generalized granular model as one of the model scenario for such an ingomogeneity where the cuprate charge subsystem remind that of Wigner crystal with the melting transition and phonon-like positional excitation modes. Formal description of R-ion relaxation coincides with that of recently suggested magnetoelastic mechanism.Comment: 4 page

Mechanical properties and formation mechanisms of a wire of single gold atoms

A scanning tunneling microscope (STM) supplemented with a force sensor is used to study the mechanical properties of a novel metallic nanostructure: a freely suspended chain of single gold atoms. We find that the bond strength of the nanowire is about twice that of a bulk metallic bond. We perform ab initio calculations of the force at chain fracture and compare quantitatively with experimental measurements. The observed mechanical failure and nanoelastic processes involved during atomic wire fabrication are investigated using molecular dynamics (MD) simulations, and we find that the total effective stiffness of the nanostructure is strongly affected by the detailed local atomic arrangement at the chain bases.Comment: To be published in Phys. Rev. Lett. 4 pages with 3 figure