Along with the growing precision in the control of matter at increasingly smaller size scales, a field of research, based onto magnetic materials of technical interest, such as bimetallic clusters, has been developed in very recent years. Thereby, here, we report on a complete study of bimetallic clusters composed of cobalt and nickel with up to 7 atoms using ab initio methods in the GGA approach. We applied an unrestricted search method based on the tensor of inertia eigenvalues to find the most stable configurations of the clusters, obtaining a diverse set of structures with different geometric properties. We explored the effect of composition on the structural properties, the chemical stability, the magnetization and the magnetic anisotropy energy (MAE) of the so-obtained systems. Our results indicate that the behavior of the clusters is mainly governed by the Co-Co interaction and to a lesser extent by the Co-Ni and Ni-Ni interactions. Furthermore, for a given cluster size the magnetic moment increases by 2 μB/Co-substitution plus 1 μB/Ni-substitution coming from the cobalt and nickel core d-states, while in some cases unpaired hybrid s-electrons can also give rise to itinerant magnetism. These features have been analyzed with the help of a Jellium model and have important consequences for the magnetism and the magnetic anisotropy of the clusters. The magnetic behavior and MAE present complex and intriguing landscapes, which suggests the possibility of finely controlling the magnetic states, by tuning the cluster composition, aiming at technical implementation in fields such as molecular magnetism or quantum computation. In particular, cases such as Co6Ni, Co4Ni3, CoNi6 Co2Ni5 and Co3Ni3 present high relative stability and enhanced magnetic moments (around 10 μB), what makes them promising candidates for applications such as subnanometer magnetic information storage.
With the advent of more precise technologies allowing manipulation of matter at nanoscopic scales and novel characterization techniques, a growing field of research is focused on magnetic materials of technical interest-such as Fe clusters-and their related physical-chemical processes. In this study, we present the results of the sequential oxidation process of the Fe cluster by considering the physical-chemistry properties of the ground state configurations of FeO ([Formula: see text]) clusters. We develop an exhaustive ab initio study into the GGA approach and explore the effect of the chemisorption of oxygen on the structural properties, the chemical stability, the magnetization and the magnetic anisotropy energy (MAE) of the systems. Our results clearly indicate that: (i) one of the studied clusters, FeO, presents the biggest electrophilicity index and the lowest chemical hardness, being the most reactive among the systems studied; (ii) the FeO exhibits a much more enhanced magnetization than other related clusters intended for health and technology applications (Sun et al 2007 J. Phys. Chem. C 111 4159-63), so that it might be a better candidate for those purposes; and (iii) the MAE presents a complex and intriguing landscape that encourages thinking about the plausible control of magnetic states focused on technical applications.
Artículo recibido el 19 de enero de 2017. Aceptado, tras revisión el 31 de julio de 2017. Publicado el 1 de septiembre de 2017. ResumenEn la comúnidad de Púlingúí perteneciente a la parroqúia de San Andrés del cantón Gúano provincia de Chimborazo, Ecúador se tratan las agúas residúales domésticas en ún sistema de tanqúes sépticos y filtro ascendente, qúe presentan problemas de mal olor y baja redúcción de la materia orgánica. El presente trabajo analiza la eficiencia de remoción de estos contaminantes al combinar el tratamiento anaerobio actúal con ún tratamiento aerobio por lodos activados en ún prototipo a escala de laboratorio. Se diseñó, constrúyó y operó ún prototipo con 27.9 litros de capacidad, de los cúales 15.8 L corresponden a la zona anaeróbica, 7.7 L a la zona de aireación y 4.4 L a la zona de sedimentación. El sistema fúe evalúado dúrante 60 días con agúa residúal doméstica proveniente de la comúnidad citada. Dúrante la evalúación se realizaron diariamente determinaciones de Ph, sólidos súspendidos y oxígeno disúelto, así mismo se determinaron dos veces por semana la Demanda Qúímica de Oxígeno (DQO). La información generada permitió observar qúe el sistema tendió a estabilizarse dúrante la semana tres de operación, alcanzando eficiencias de remoción de materia orgánica en términos de DQO en el tratamiento anaeróbico de 53 %, en el tratamiento aeróbico de 75 %, logrando úna redúcción total en todo el sistema del 88 % y eliminando el olor. Con datos del tanqúe anaeróbico tomados despúés de 60 días de trabajo continúo, se permitió proyectar el mantenimiento de la planta de tratamiento de Púlinguí el mismo qúe debe realizarse en aproximadamente cada 4 años. Palabras claves:Tratamiento de aguas residuales, anaeróbico, aeróbico, tanque séptico, lodos activados, carga contaminante.
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