AFLOW-QHA3P: Robust and automated method to compute thermodynamic properties of solids

Accelerating the calculations of finite-temperature thermodynamic properties is a major challenge for rational materials design. Reliable methods can be quite expensive, limiting their applicability in autonomous high-throughput workflows. Here, the three-phonon quasiharmonic approximation (QHA) method is introduced, requiring only three phonon calculations to obtain a thorough characterization of the material. Leveraging a Taylor expansion of the phonon frequencies around the equilibrium volume, the method efficiently resolves the volumetric thermal expansion coefficient, specific heat at constant pressure, the enthalpy, and bulk modulus. Results from the standard QHA and experiments corroborate the procedure, and additional comparisons are made with the recently developed self-consistent QHA. The three approaches—three-phonon, standard, and self-consistent QHAs—are all included within the open-source ab initio framework aflow, allowing the automated determination of properties with various implementations within the same framework

Coordination corrected ab initio formation enthalpies

The correct calculation of formation enthalpy is one of the enablers of ab-initio computational materials design. For several classes of systems (e.g. oxides) standard density functional theory produces incorrect values. Here we propose the “coordination corrected enthalpies” method (CCE), based on the number of nearest neighbor cation–anion bonds, and also capable of correcting relative stability of polymorphs. CCE uses calculations employing the Perdew, Burke and Ernzerhof (PBE), local density approximation (LDA) and strongly constrained and appropriately normed (SCAN) exchange correlation functionals, in conjunction with a quasiharmonic Debye model to treat zero-point vibrational and thermal effects. The benchmark, performed on binary and ternary oxides (halides), shows very accurate room temperature results for all functionals, with the smallest mean absolute error of 27(24) meV/atom obtained with SCAN. The zero-point vibrational and thermal contributions to the formation enthalpies are small and with different signs—largely canceling each other

AFLOW-SYM: platform for the complete, automatic and self-consistent symmetry analysis of crystals

Determination of the symmetry profile of structures is a persistent challenge in materials science. Results often vary amongst standard packages, hindering autonomous materials development by requiring continuous user attention and educated guesses. This article presents a robust procedure for evaluating the complete suite of symmetry properties, featuring various representations for the point, factor and space groups, site symmetries and Wyckoff positions. The protocol determines a system-specific mapping tolerance that yields symmetry operations entirely commensurate with fundamental crystallographic principles. The self-consistent tolerance characterizes the effective spatial resolution of the reported atomic positions. The approach is compared with the most used programs and is successfully validated against the space-group information provided for over 54 000 entries in the Inorganic Crystal Structure Database (ICSD). Subsequently, a complete symmetry analysis is applied to all 1.7+ million entries of the AFLOW data repository. The AFLOW-SYM package has been implemented in, and made available for, public use through the automated ab initio framework AFLOW

ANÁLISIS GEOGRÁFICO DEL ESPACIO URBANO DEL DISTRITO DE LA CHORRERA

Work on the geographical analysis of urban space, is a study of urban development, in the districts that make up the head of our district. We have seen how in recent decades the geographic space has been modified to make way for an uncontrolled, unplanned urbanization, environmental regulations and producing in our city a collapse of basic services product of high demand due to population increase, we also see how the environment has been degraded through deforestation mulched areas, which have been destroyed to make way for developments, other environmental problems are the collapse of the municipal landfill and cutting mangrove areas, areas prone to natural disasters like floods and mudslides In this work, a quantitative methodology was used, as there is a relationship whose nature is representable by a numerical model either linear, exponential or the like because the demographic phenomena that have occurred in the city of La Chorrera m the last decade are analyzed. Research techniques were also developed as office work, field research and the application of geomatics methods and the use of Geographic Information Systems (GIS). This study presents a series of conclusions and recommendations which the current situation of the problem is and what measures can be implemented to solve it.  El trabajo sobre el análisis geográfico del espacio urbano es un estudio del desarrollo urbanístico, en los corregimientos que conforman la cabecera del distrito de Panamá Oeste. Se ha visto como en las últimas décadas el espacio geográfico ha sido modificado para dar paso a un urbanismo descontrolado sin planificación, ni normativas ambientales produciendo en nuestra ciudad un colapso de los servicios básicos producto de la alta demanda por el aumento poblacional, también vemos cómo el ambiente ha sido degrado con la deforestación de zonas con cobertura vegetal, las cuales han sido destruidas para dar paso a urbanizaciones, otros problemas ambientales son el colapso, del vertedero municipal y la tala de zonas de manglares, áreas propensas a desastres naturales como inundaciones y deslaves. En este trabajo se utilizó una metodología cuantitativa, ya que existe una relación cuya naturaleza sea representable por algún modelo numérico ya sea lineal, exponencial o similar, porque se analizan los fenómenos demográficos que se han dado en la ciudad de La Chorrera en la última década. También se desarrollaron técnicas de investigación como el trabajo de gabinete, investigación de campo y la aplicación de métodos geomáticos como la utilización de Sistemas de Información Geográfica (S I G). En este estudio se presenta una serie de conclusiones y recomendaciones, donde se plantea la situación actual del problema y qué medidas se pueden implementar para solucionarlo

AFLOW-CHULL: Cloud-Oriented Platform for Autonomous Phase Stability Analysis

A priori prediction of phase stability of materials is a challenging practice, requiring knowledge of all energetically-competing structures at formation conditions. Large materials repositories - housing properties of both experimental and hypothetical compounds - offer a path to prediction through the construction of informatics-based, ab-initio phase diagrams. However, limited access to relevant data and software infrastructure has rendered thermodynamic characterizations largely peripheral, despite their continued success in dictating synthesizability. Herein, a new module is presented for autonomous thermodynamic stability analysis implemented within the open-source, ab-initio framework AFLOW. Powered by the AFLUX Search-API, AFLOW-CHULL leverages data of more than 1.8 million compounds currently characterized in the AFLOW.org repository and can be employed locally from any UNIX-like computer. The module integrates a range of functionality: the identification of stable phases and equivalent structures, phase coexistence, measures for robust stability, and determination of decomposition reactions. As a proof-of-concept, thorough thermodynamic characterizations have been performed for more than 1,300 binary and ternary systems, enabling the identification of several candidate phases for synthesis based on their relative stability criterion - including 18 promising C15b-type structures and two half-Heuslers. In addition to a full report included herein, an interactive, online web application has been developed showcasing the results of the analysis, and is located at aflow.org/aflow-chull

The AFLOW Fleet for Materials Discovery

The traditional paradigm for materials discovery has been recently expanded to incorporate substantial data driven research. With the intent to accelerate the development and the deployment of new technologies, the AFLOW Fleet for computational materials design automates high-throughput first principles calculations, and provides tools for data verification and dissemination for a broad community of users. AFLOW incorporates different computational modules to robustly determine thermodynamic stability, electronic band structures, vibrational dispersions, thermo-mechanical properties and more. The AFLOW data repository is publicly accessible online at aflow.org, with more than 1.7 million materials entries and a panoply of queryable computed properties. Tools to programmatically search and process the data, as well as to perform online machine learning predictions, are also available.Comment: 14 pages, 8 figure