Parallel eigensolvers in plane-wave Density Functional Theory

We consider the problem of parallelizing electronic structure computations in plane-wave Density Functional Theory. Because of the limited scalability of Fourier transforms, parallelism has to be found at the eigensolver level. We show how a recently proposed algorithm based on Chebyshev polynomials can scale into the tens of thousands of processors, outperforming block conjugate gradient algorithms for large computations

Sugerencia o realidad

Treballs Finals de Grau de Belles Arts. Facultat de Belles Arts. Universitat de Barcelona, Curs: 2017, Tutor: Gloria Muñoz Pfister[spa] En este trabajo de final de grado, quiero proponer la reflexión sobre los cánones de belleza que se han ido estableciendo a lo largo de la historia y expresar una nueva perspectiva sobre cómo entender la belleza desde diferentes vertientes. ¿Qué se define realmente como belleza?¿Qué es la belleza?¿Cómo lo afrontamos?¿Dónde radica? ¿Cuál es la correcta y cual no?¿La belleza es puramente física? A lo largo de la historia los cánones de belleza, siempre variables y únicos en cada una de las culturas, se han entendido como el conjunto de características, que una sociedad considera como hermoso o atractivo, reunidas en una persona u objeto. Mi objetivo a tratar con mi proyecto de final de grado, es el de cambiar totalmente el punto de vista o la idea errónea que se tiene de belleza establecida actualmente en nuestra sociedad y hacer ver a cualquier individuo, que la belleza no radica solamente en el mero físico de un ser humano u objeto, ya que mi royecto realmente estará muy enfocado en expresar una mirada más hacia la belleza interior del ser humano y en rechazar la idea de la belleza física de las personas. Es decir, quiero expresar mi proyecto final mediante la reflexión del concepto de belleza, que es muy amplio y hay muchos tipos de variantes y de significados, mediante el trabajo escrito y creando una serie decomposiciones pictóricas realistas, expresando la dicha idea en que la belleza no radica en el cuerpo del humano sino en el interior de éste y de lo que nos transmite con su mirada.[eng] In this work, I want to propose a reflection on the canons of beauty that have been established throughout history and express a new perspective on how to understand beauty from different perspectives. What is really defined as beauty? What is beauty? How do we deal with it? Where do you live? Which one is right and which is not? Is beauty purely physical? Throughout history the canons of beauty, always variable and unique in each of the cultures, have been understood as the set of characteristics, which a society considers as beautiful or attractive, gathered in a person or object. My goal to deal with my final grade project is to totally change the point of view or the mistaken idea of beauty that is currently established in our society and make any individual see that beauty does not lie only in the Mere physical of a human being or object, since my project will really be very focused on expressing a closer look at the inner beauty of the human being and at rejecting the idea of the physical beauty of people. That is, I want to express my final project by reflecting the concept of beauty, which is very broad and there are many types of variants and meanings, through written work and creating a series of realistic pictorial compositions, expressing the said idea in which the Beauty lies not in the human body but in the interior of it and what it transmits with its eyes

Strong Isotopic Effect in Phase II of Dense Solid Hydrogen and Deuterium

Quantum nuclear zero-point motions in solid H$_2$ and D$_2$ under pressure are investigated at 80 K up to 160 GPa by first-principles path-integral molecular dynamics calculations. Molecular orientations are well-defined in phase II of D$_2$, while solid H$_2$ exhibits large and very asymmetric angular quantum fluctuations in this phase, with possible rotation in the (bc) plane, making it difficult to associate a well-identified single classical structure. The mechanism for the transition to phase III is also described. Existing structural data support this microscopic interpretation.Comment: 5 pages, 3 figure

A wavelet-based Projector Augmented-Wave (PAW) method: reaching frozen-core all-electron precision with a systematic, adaptive and localized wavelet basis set

We present a Projector Augmented-Wave~(PAW) method based on a wavelet basis set. We implemented our wavelet-PAW method as a PAW library in the ABINIT package [http://www.abinit.org] and into BigDFT [http://www.bigdft.org]. We test our implementation in prototypical systems to illustrate the potential usage of our code. By using the wavelet-PAW method, we can simulate charged and special boundary condition systems with frozen-core all-electron precision. Furthermore, our work paves the way to large-scale and potentially order-N simulations within a PAW method

Narrowband filtering for atom-resonant photon pair generation

En col·laboració amb la Universitat Autònoma de Barcelona (UAB) i la Universitat de Barcelona (UB)In this master's thesis we study two filtering techniques, first the Faraday anomalous dispersion optical filter (FADOF) and second a monolithic Fabry-Pérot interferometer with the aim of filtering down-converted photon pairs resonant with the D1 line of 87Rb. The geometrical properties of a plano-convex lens with a high- refectivity dielectric coating applied on both sides provides us with a long term stability and a tunable Fabry-Pérot cavity suitable for narrowband frequency filtering. A transmission of 30% is reached, a free spectral range of 19.2 GHz and a bandwidth of 47.5 MHz are measured providing a proof-of-concept for a future implementation. In addition, a 852 nm DFB laser is mounted and tested by performing saturated absorption spectroscopy with the aim of locking the laser. However, the results show that the laser was mode hopping

Estudi de viabilitat d'una empresa de reforços de formigó amb materials compostos

CATALÀ: El present projecte neix amb la idea del responsable del Laboratori per la Innovació Tecnològica d’Estructures i Materials (LITEM) de crear una empresa relacionada amb el reforç d’estructures de formigó amb materials compostos, específicament amb fibra de carboni. L’elaboració del estudi de viabilitat de l’empresa ha estat dut a terme com a projecte final de carrera d’enginyeria en organització industrial. La rehabilitació ha estat un dels subsectors del sector de la construcció que menys s’ha vist afectat per la crisis actual i un dels que es pretén fomentar per reactivar el sector. En l’anàlisi de mercat, es veurà en quin punt es troba el subsector, quines són les oportunitats d’aquest de cara al futur així com els factors de l’empresa, tan interns com externs, que permetran elaborar un anàlisi DAFO i veure la situació de l’empresa respecte el mercat. Fet l’anàlisi de mercat, s’avaluaran diferents propostes de serveis que l’empresa podria oferir i es determinarà quins d’aquests poden aportar el màxim d’avantatges als clients de l’empresa a l’hora que satisfan les necessitats actuals del mercat. Definits aquests serveis, es farà una descripció del negoci de l’empresa, s’explicarà com es gestionarà la qualitat i l’impacte mediambiental, es seleccionarà la forma jurídica i es seleccionarà un nom per l’empresa. Posteriorment, es definirà una estratègia de màrqueting que permetrà promocionar els serveis de l’empresa seguint unes directrius bàsiques i a partir de la qual es farà una previsió de vendes. Seguidament, es definirà l’estructura de recursos humans necessària per oferir els serveis seleccionats i cobrir les previsions calculades i es realitzarà un estudi econòmic i financer que permetrà veure la viabilitat econòmica del projecte i els beneficis que obtindrà derivats de la seva activitat. El pla de contingències especificarà els procediments a seguir en cas que es donés algun factor que alteres el previst i s’acabarà amb unes conclusions sobre la viabilitat de l’empresa proposada.CASTELLÀ: El presente proyecto nace con la idea del responsable del Laboratorio para la Innovación Tecnológica de Estructuras y Materiales (LITEM) de crear una empresa relacionada con el refuerzo de estructuras de hormigón con materiales compuestos, específicamente con fibra de carbono. La elaboración del estudio de viabilidad de la empresa ha sido llevada a cabo como proyecto final de carrera de ingeniería en organización industrial. La rehabilitación ha sido uno de los subsectores del sector de la construcción que menos se ha visto afectado por la crisis actual y uno de los que se pretende fomentar para reactivar el sector. En el análisis de mercado, se verá en qué punto se encuentra el subsector, cuáles son las oportunidades de este de cara al futuro así como los factores de la empresa, tanto internos como externos, que permitirán elaborar un análisis DAFO y ver la situación de la empresa respecto al mercado. Hecho el análisis de mercado, se evaluarán diferentes propuestas de servicios que la empresa podría ofrecer y se determinará cuáles de estos pueden aportar el máximo de ventajas a los clientes de la empresa a la vez que satisfacen las necesidades actuales del mercado. Definidos estos servicios, se hará una descripción del negocio de la empresa, se explicará cómo se gestionará la calidad y el impacto medioambiental, se seleccionará la forma jurídica y se seleccionará un nombre para la empresa. Posteriormente, se definirá una estrategia de marketing que permitirá dar a conocer los servicios de la empresa siguiendo unas directrices básicas y a partir de la cual se hará una previsión de ventas. Seguidamente, se definirá la estructura de recursos humanos necesaria para ofrecer los servicios seleccionados y cubrir las previsiones calculadas y se realizará un estudio económico y financiero que permitirá ver la viabilidad económica del proyecto y los beneficios que obtendrá derivados de su actividad. El plan de contingencias especificará los procedimientos a seguir en caso de que se diera algún factor que alterase lo previsto y se acabará con unas conclusiones sobre la viabilidad de la empresa propuesta.ANGLÈS: The present project was created above the idea of the responsible of the Laboratory for the Technological Innovation of Structures and Materials (LITEM) of creating a company related to the reinforcement of concrete structures with composite materials, specifically carbon fiber. The preparation of the feasibility study of the company has been carried out as the final degree project for Management Engineering. Rehabilitation has been one of the subsectors of the construction sector that has been less affected by the current crisis and the key one to revive the sector. In the market analysis, the subsector situation will be seen, it will show what are the market opportunities and it will also show the factors of the company, internal and external, which will help to create a SWOT analysis and see the situation of the company with respect to the market. Once the market analysis has been done, there will be an assessment of various services that the company could offer and it will be determined which of these may have the maximum benefits to enterprise customers while they meet the current needs of market. Defined these services, there will be a description of the business of the company, an explanation on how to manage the quality and environmental impact will be done, the legal form of the company will be decided and the selection of the name of the company will be arranged. Afterwards, a marketing strategy will be defined with the intention of promoting the company's services following some basic guidelines and from which there will be a sales forecast. Later on, the structure of human resources required to deliver the selected services and meet the expectations calculated will be defined and there will be an economic and financial viability study which will show the benefits of the project and the company activity. The contingency plan will specify the procedures to follow if there were given any factors that altered the schedule and it will finish with some conclusions about the feasibility of the proposed company

Density functional perturbation theory within non-collinear magnetism

We extend the density functional perturbation theory formalism to the case of non-collinear magnetism. The main problem comes with the exchange-correlation (XC) potential derivatives, which are the only ones that are affected by the non-collinearity of the system. Most of the present XC functionals are constructed at the collinear level, such that the off-diagonal (containing magnetization densities along $x$ and $y$ directions) derivatives cannot be calculated simply in the non-collinear framework. To solve this problem, we consider here possibilities to transform the non-collinear XC derivatives to a local collinear basis, where the $z$ axis is aligned with the local magnetization at each point. The two methods we explore are i) expanding the spin rotation matrix as a Taylor series, ii) evaluating explicitly the XC for the local density approximation through an analytical expression of the expansion terms. We compare the two methods and describe their practical implementation. We show their application for atomic displacement and electric field perturbations at the second order, within the norm-conserving pseudopotential methods

Dipolar localization of waves in twisted phononic crystal plates

The localization of waves in two-dimensional clusters of scatterers arranged in relatively twisted lattices is studied by multiple scattering theory. It is found that, for a given frequency, it is always possible to nd localized modes for a discrete set of rotation angles, analogous to the so-called \magic angles" recently found in two-dimensional materials like graphene. Similarly, for small rotations of the lattices, a large number of resonant frequencies is found, whose position strongly depends on the rotation angle. Moreover, for angles close to those that make the two lattices commensurable a single mode appears that can be easily tuned by the rotation angle. Unlike other twisted materials, where the properties of the bilayers are mainly explained in terms of the dispersion relation of the individual lattices, the special angles in these clusters happen because of the formation of dipolar scatterers due to the relative rotation between the two lattices, enhancing therefore their interaction. While the presented results are valid for any type of wave, the speci c case of exural waves in thin elastic plates is numerically studied, and the di erent modes found are comprehensively explained in terms of the interaction between pairs of scatterers. The analysis presented here shows that these structures are promising candidates for the inverse design of tunable wave-trapping devices for classical waves