Economic and environmental assessment of directly converting CO2 into a gasoline fuel

The threat posed by Climate Change demands urgent action on finding clean energy solutions with a view to cutting fossil fuel consumption. However, a sudden stop in the use of fossil fuels is not possible without a profound disruption of the economy. This transition is expected to take several decades, and therefore every type of renewable energy should be considered as part of the solution mix. In this work, we propose including gasoline synthesized from atmospheric CO2 as one possible interim solution while the transition away from liquid fossil fuels intensifies. To that end, we have designed a novel process that produces green gasoline in one stage on an industrial scale. This contrasts with the two or three stages needed in the classical Fischer-Tropsch based processes. Furthermore, we have optimized this process through mass and heat integration, and propose three different options that make the most of the waste streams. Finally, we have studied a total of 144 realistic scenarios that take into account the origin of H2 and CO2 as well as their environmental impacts and costs. According to our findings, such a process will be capable of producing high-quality gasoline to be manufactured competitively in the near future. The significance of our findings is that it is realistic to reduce carbon emissions while also promoting the circular economy.The authors J.A.C and M.J.F.T thank Generalitat Valenciana for the financial support under the project PROMETEO 2020/064

Refined electron-spin transport model for single-element ferromagnetic systems: Application to nickel nanocontacts

Through a combination of atomistic spin-lattice dynamics simulations and relativistic ab initio calculations of electronic transport we shed light on unexplained electrical measurements in nickel nanocontacts created by break junction experiments under cryogenic conditions (4.2 K). We implement post-self-consistent-field corrections in the conductance calculations to account for spin-orbit coupling and the noncollinearity of the spins, resulting from the spin-lattice dynamics. We find that transverse magnetic domain walls are formed preferentially in (111)-oriented face-centered-cubic nickel atomic-sized contacts, which also form elongated constrictions, giving rise to enhanced individual domain wall magnetoresistance. Our calculations show that the ambiguity surrounding the conductance of a priori uniformly magnetized nickel nanocontacts can be traced back to the crystallographic orientation of the nanocontacts, rather than spontaneously formed magnetic domain walls “pinned” at their narrowest points.This work was supported by the Generalitat Valenciana through Grant No. PROMETEO2017/139. C.S. gratefully acknowledges financial support from the Dean Fellowship of the Weizmann Institute of Science and Generalitat Valenciana (Grant No. CDEIGENT2018/028). O.T. appreciates the support of the Harold Perlman family, and acknowledges funding by a research grant from Dana and Yossie Hollander, the Israel Science Foundation (Grant No. 1089/15), the Minerva Foundation (Grant No. 120865), and The Ministry of Science and Technology of Israel (Grant No. 3-16244). J.J.P. acknowledges financial support from Spanish MINECO through Grants No. FIS2016-80434-P and No. PID2019-109539GB-C43, the Fundación Ramón Areces, the María de Maeztu Program for Units of Excellence in R&D (Grant No. CEX2018-000805-M), the Comunidad Autónoma de Madrid through the Nanomag COST-CM Program (Grant No. S2018/NMT-4321), the European Union Seventh Framework Programme under Grant Agreement No. 604391 Graphene Flagship, the Centro de Computación Científica of the Universidad Autónoma de Madrid and the computer resources at MareNostrum and the technical support provided by the Barcelona Supercomputing Center (Grant No. FI-2019-2-0007). The SLD and DFT calculations in this paper were performed on the high-performance computing facilities of the University of Alicante and the University of South Africa

Dynamic bonding influenced by the proximity of adatoms to one atom high step edges

Low-temperature scanning tunneling microscopy is used here to study the dynamic bonding of gold atoms on surfaces under low coordination conditions. In the experiments, using an atomically sharp gold tip, a gold adatom is deposited onto a gold surface with atomic precision either on the first hollow site near a step edge or far away from it. Classical molecular dynamics simulations at 4.2 K and density-functional theory calculations serve to elucidate the difference in the bonding behavior between these two different placements, while also providing information on the crystalline classification of the STM tips based on their experimental performance.This work was supported by the Generalitat Valenciana through Grants No. CDEIGENT/2018/028, No. PROMETEO/2017/139, and No. PROMETEO/2021/017. The authors also acknowledge financial support from Spanish MICIN through Grant No. PID2019-109539 GB-C43, the María de Maeztu Program for Units of Excellence in R&D (Grant No. CEX2018-000805-M), the Comunidad Autónoma de Madrid through the Nanomag COST-CM Program (Grant No. S2018/NMT-4321). The theoretical modeling was performed on the high-performance computing facilities of the University of South Africa and the University of Alicante. Netherlands Organization for Scientific Research (NWO/OCW) supported the experiments

Experiències senzilles de física recreativa: flascó de Mariotte, refracció de la llum i tira d’alumini ondulant

En aquest treball presentem una sèrie d’experiments senzills i estimulants de física que resulten útils per a reforçar els coneixements propis d’aquesta matèria, consolidar conceptes físics, captar l’atenció dels estudiants i fomentar-ne l’interès per la matèria de física. En aquesta ocasió hem dissenyat i dut a terme experiències de diversos camps de la Física, com ara fluids (flascó de Mariotte), òptica (refracció de la llum) i magnetisme (tira d’alumini ondulant a causa d’un camp magnètic). Amb aquest tipus d’experiments simples volem augmentar la motivació dels estudiants cap a la matèria de física, ja que l’objectiu d’aquestes experiències és tractar d’entendre el fenomen que s’està observant, en comptes d’obtenir i tractar dades. Aquests experiments estan adreçats als estudiants dels primers cursos dels graus de ciències i de les diverses enginyeries. Aquesta manera d’introduir conceptes de física mitjançant experiments sorprenents fa que l’aprenentatge resulte més significatiu, i constitueixen una eina pedagògica de gran ajuda en el procés d’ensenyament-aprenentatge de la física

Dynamic bonding of metallic nanocontacts: Insights from experiments and atomistic simulations

The conductance across an atomically narrow metallic contact can be measured by using scanning tunneling microscopy. In certain situations, a jump in the conductance is observed right at the point of contact between the tip and the surface, which is known as “jump to contact” (JC). Such behavior provides a way to explore, at a fundamental level, how bonding between metallic atoms occurs dynamically. This phenomenon depends not only on the type of metal but also on the geometry of the two electrodes. For example, while some authors always find JC when approaching two atomically sharp tips of Cu, others find that a smooth transition occurs when approaching a Cu tip to an adatom on a flat surface of Cu. In an attempt to show that all these results are consistent, we make use of atomistic simulations; in particular, classical molecular dynamics together with density functional theory transport calculations to explore a number of possible scenarios. Simulations are performed for two different materials: Cu and Au in a [100] crystal orientation and at a temperature of 4.2 K. These simulations allow us to study the contribution of short- and long-range interactions to the process of bonding between metallic atoms, as well as to compare directly with experimental measurements of conductance, giving a plausible explanation for the different experimental observations. Moreover, we show a correlation between the cohesive energy of the metal, its Young's modulus, and the frequency of occurrence of a jump to contact.W. Dednam acknowledges support from the National Research Foundation of South Africa through the Scarce Skills Masters scholarship funding programme (Grant Unique Number 92138). This work is supported by the Generalitat Valenciana through Grant Reference PROMETEO2012/011 and MINECO under Grant No. FIS2013-47328, by European Union structural funds and the Comunidad de Madrid Programs S2013/MIT-3007 and P2013/MIT-2850. This work is also part of the research programme of the Foundation for Fundamental Research on Matter (FOM), which is financially supported by the Netherlands Organisation for Scientific Research (NWO)

Directional bonding explains the high conductance of atomic contacts in bcc metals

Atomic-sized contacts of iron, created in scanning tunneling microscope break junctions, present unusually high values of conductance compared to other metals. This result is counterintuitive since, at the nanoscale, body-centered-cubic metals are expected to exhibit lower coordination than face-centered-cubic metals. In this work we first perform classical molecular dynamics simulations of the contact rupture, using two different interatomic potentials. The first potential is isotropic, and produces mostly single-atom prerupture contacts. The second potential accounts for the directional bonding in the materials, and produces mostly highly coordinated prerupture structures, generally consisting of more than one atom in contact. To compare the two different types of structures with experiments, we use them as input to density functional theory electronic transport calculations of the conductance. We find that the highly coordinated structures, obtained from the anisotropic potential, yield higher conductances which are statistically in better agreement with those measured for body-centered-cubic iron. We thus conclude that the directional bonding plays an important role in body-centered-cubic metals.This work was supported by the Generalitat Valenciana through PROMETEO2017/139 and GENT (CDEIGENT2018/028), the Spanish government through Grants No. MAT2016-78625-C2-1-P and No. FIS2016-80434-P, and the Spanish Ministry of Science and Innovation, through the “María de Maeztu” Programme for Units of Excellence in R&D (CEX2018-000805-M), by Comunidad Autónoma de Madrid through Grant No. S2018/NMT-4321 (NanomagCOST-CM), by the Fundación Ramón Areces, and by the European Union Graphene Flagship under Grant No. 604391

Role of first-neighbor geometry in the electronic and mechanical properties of atomic contacts

We study in detail, via experimental measurements, atomistic simulations, and density functional theory transport calculations, the process of formation and the resulting electronic properties of atomic-sized contacts made of Au, Ag, and Cu. Our data analysis of both experimental results and simulations leads to a precise relationship between geometry and electronic transmission—we reestablish the significant influence of the number of first neighbors on the electronic properties of atomic-sized contacts. This result allows us also to interpret subtle differences between the metals during the process of contact formation as well as the characteristics of the resulting contacts.This work has been funded from the Spanish Ministerio de Educación y Ciencia through Grants No. FIS2013-47328 and No. MAT2016-78625 and the Conselleria d’Educació, Investigació, Cultura i Esport de la Generalitat Valenciana, PROMETEO/2017/139. C.S. gratefully acknowledges financial support from SEPE Servicio Público de Empleo Estatal. W.D. acknowledges funding from the National Research Foundation of South Africa through the Innovation Doctoral scholarship programme, Grant UID 102574

Influence of Relativistic Effects on the Contact Formation of Transition Metals

Our analysis of the contact formation processes undergone by Au, Ag, and Cu nanojunctions reveals that the distance at which the two closest atoms on a pair of opposing electrodes jump into contact is, on average, 2 times longer for Au than either Ag or Cu. This suggests the existence of a longer-range interaction between those two atoms in the case of Au, a result of the significant relativistic energy contributions to the electronic structure of this metal, as confirmed by ab initio calculations. Once in the contact regime, the differences between Au, Ag, and Cu are subtle, and the conductance of single-atom contacts for metals of similar chemical valence is mostly determined by geometry and coordination.This work has been funded by the Spanish Government through Grants No. FIS2013-47328 and No. MAT2016-78625 and the Conselleria d’Educació, Investigació, Cultura i Esport de la Generalitat Valenciana, PROMETEO/2017/139. C. S. gratefully acknowledges financial support from SEPE Servicio Público de Empleo Estatal. W. D. acknowledges funding from the National Research Foundation of South Africa through the Innovation Doctoral scholarship programme, Grant No. UID 102574

Experiències senzilles de física recreativa: Conservació del moment lineal, efecte Coandă i emissió atòmica

La realització pràctica d’experiments és fonamental en qualsevol disciplina científica. Per això, en aquest treball exposem una sèrie d’experiències de física senzilles i sorprenents que ens permetran reforçar diversos conceptes físics d’una manera amena, utilitzant materials molt assequibles i barats. Amb la realització d’aquests experiments volem estimular la curiositat de l’alumnat i el plaer per la investigació i el descobriment de nous fenòmens físics. Aquestes experiències estan adreçades tant a estudiants d’educació secundària i batxillerat com a alumnes dels primers cursos d’universitat. Hem dissenyat i dut a terme experiències de diversos camps de la física, entre els quals hi ha algunes pràctiques per a posar de manifest la conservació del moment lineal, o l’efecte Coandă en fluids en moviment, i també experiments de física atòmica relacionats amb l’emissió atòmica en l’espectre visible, que posen de manifest la quantització de l’energia dels nivells atòmics. Amb aquestes experiències volem motivar els alumnes en l’estudi i l’interès per la física des d’una perspectiva diferent de l’habitual

Experiències senzilles d’electromagnetisme: Atracció i repulsió per forces magnètiques. Caiguda d’imant a càmera lenta

La realització d’experiments científics és una activitat pedagògica que afavoreix l’aprenentatge significatiu dels alumnes, la seua motivació per la matèria i estimula l’interès per ampliar coneixements. En aquest treball presentem dues experiències senzilles de fenòmens d’inducció electromagnètica, amb el propòsit que els estudiants comprenguen els principals conceptes involucrats i l’estreta relació entre l’electricitat i el magnetisme. El nivell d’aquests experiments és adequat per a segon curs de batxillerat, per a qualsevol curs introductori de Física en els Graus de Ciències i per a l’alumnat del Màster d’Educació Secundària