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.
Extensive evidence has documented the moderating role of design attributes in crowding; yet, the effect of public transportation design on travel experience has been overlooked. We conducted a ...within-design experimental study aimed to estimate the buffering role of design resources in both subjective experience (crowding, pleasantness, stimulation, and dominance) and behavioral responses (patterns of eye movements) to crowded conditions on a bus. Three physical bus elements (seat demarcation, access to the window, outdoor surrounding) and their degree of supportiveness (poor, moderate, high) were manipulated. The results of Phase 1 (N = 80) and Phase 2 (N = 33) confirmed the beneficial moderating effect of the three physical components on crowding and their compensatory role. The adopted multimethodological approach confirmed to be an ecologically valid strategy for studying the effects of the physical environment on human behavior. Practical implications and directions for future research are discussed.
Activated bentonites are low-cost acid catalysts used in several reactions. However, their application at an industrial scale is affected by the formation of colloidal suspensions when these ...bentonites are in aqueous solutions. In order to overcome these limitations, this work proposes obtaining a catalyst based on a composite containing natural bentonite within a silica–resin structure, which allows separating and re-utilizing the catalyst more easily and without centrifugal filtration requirements. By means of characterization techniques, the present study determined that the activated bentonite composite presented a total specific surface area of ~360 m2 g−1, ~4 mmol of acid sites per gram of bentonite, and sites with strong acid strength, all of which bestowed activity and selectivity in the solketal synthesis reaction from glycerol and acetone, reaching equilibrium conversion within a short reaction time. Furthermore, the present work developed a Langmuir–Hinshelwood–Hougen–Watson kinetic model, achieving an activation energy of 50.3 ± 3.6 kJ mol−1 and a pre-exponential factor of 6.4 × 106 mol g−1 L−1 s−1, which are necessary for reactor design.
Constrained DFT for Molecular Junctions Zotti, Linda Angela; Dednam, Wynand; Lombardi, Enrico B ...
Nanomaterials (Basel, Switzerland),
04/2022, Letnik:
12, Številka:
7
Journal Article
Recenzirano
Odprti dostop
We have explored the use of constrained density functional theory (cDFT) for molecular junctions based on benzenediamine. By elongating the junction, we observe that the energy gap between the ...ionization potential and the electronic affinity increases with the stretching distance. This is consistent with the trend expected from the electrostatic screening. A more detailed analysis shows how this influences the charge distribution of both the individual metal layers and the molecular atoms. Overall, our work shows that constrained DFT is a powerful tool for studying screening effects in molecular junctions.
In recent years, a growing number of countries have adopted constitutional provisions requiring that state law be consistent with Islamic law (sharia). Muslims today are deeply divided about what ...types of state action are consistent with sharia. The impact of a "Sharia guarantee clause" (SGC) depends largely on questions of constitutional design: who is given the power to interpret and apply the provision and what procedures do they follow? This article explores the trends that gave rise to SGCs and provides a history of their incorporation into national constitutions. It then surveys a number of the remarkably varied schemes that countries have developed to interpret and enforce their SGCs, and it considers the impact that different schemes have had on society. Finally, building on this background, the article considers what types of SGC enforcement scheme, if any, are consistent with democracy. As it notes, SGCs are often found in authoritarian or imperfectly democratic constitutions. Unsurprisingly, the designers of SGC enforcement schemes in non-democratic countries have generally tried to ensure that their SGC will be interpreted and applied in a way that permitted or even promoted non-democratic policies. Nevertheless, from the experience of non-democratic countries with SGCs we can draw some important lessons about the types of SGC enforcement scheme that would allow more democratic states to promote both democratic political participation and rights. Furthermore, recent debates have erupted in Western liberal democracies about how best to reconcile rights enforcement with democracy. These help to further clarify some issues that aspirational Islamic democracies will face as they try to develop SGC enforcement schemes for a democratic society, and they provide insights into the qualities that an institution must possess if it is to address these issues effectively. A number of Muslim countries are currently debating how best to square a constitutional commitment to respect Islam with parallel commitments to democracy and rights. Acknowledging that these countries will need to tailor their SGC enforcement schemes to very different local conditions, this article describes some basic design features that effective democratic SGC enforcement schemes are likely to share.
Low density and high breakage resistance ceramic proppants were developed from kaolin, bauxite and monoaluminum phosphate (MAP). The effect of the particle size on the raw materials over the density, ...the open porosity and the breakage resistance of the proppants was evaluated. The phase composition and the structure of the proppants due to the milling process were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and pore size distribution by mercury intrusion. The proppants obtained with raw materials of smaller size improved its breakage resistance and developed a smaller open pore size, achieving an apparent density of 2.4g/cm3 with a breakage ratio of 9.61% under 64MPa. Some properties of the AG3 proppants with sand, low density ceramic proppants of the literature and commercial low density ceramics proppants were compared.
•Low density ceramic proppants were prepared from kaolin and bauxite.•The milling of the raw materials influences on the porosity and breakage resistance.•The obtained proppants presents the apparent density in the range of 2.32–2.4g/cm3.•The lowest breakage ratio of the proppants was 9.61% under 64MPa.
Although diamond has been successfully n-type doped with phosphorus, the search for shallower n-type dopants in diamond has continued. Interstitial Li and Na have been predicted to be shallow donors, ...however, experimental results have been contradictory. Aluminum, if incorporated, may be expected to form an acceptor in the same way as boron, and it too was modeled here. We report
ab initio Density Functional Theory modeling of Li, Na and Al in diamond and show that although interstitial lithium and sodium are shallow donors, interstitial Li will readily diffuse and that it is favorable for migrating Li to be trapped at vacancies. The resulting substitutional Li is not only passivated but also compensates remaining interstitial donors, explaining the high resistivity or electrical inactivity observed in Li doped diamond. Na is shown to be most stable as a substitutional acceptor, in agreement with Na diffusing as a negative ion in diamond. Substitutional aluminum is found to induce a deep acceptor level in the band gap, much deeper than the boron acceptor level, inducing greater distortion of the host lattice.
In the field of molecular electronics, especially in quantum transport experiments, determining the geometrical configurations of a single molecule trapped between two electrodes can be challenging. ...To address this challenge, we employed a combination of molecular dynamics (MD) simulations and electronic transport calculations based on density functional theory to determine the molecular orientation in our break-junction experiments under ambient conditions. The molecules used in this study are common solvents used in molecular electronics, such as benzene, toluene (aromatic), and cyclohexane (aliphatic). Furthermore, we introduced a novel criterion based on the normal vector of the surface formed by the cavity of these ring-shaped monocyclic hydrocarbon molecules to clearly define the orientation of the molecules with respect to the electrodes. By comparing the results obtained through MD simulations and density functional theory with experimental data, we observed that both are in good agreement. This agreement helps us to uncover the different geometrical configurations that these molecules adopt in break-junction experiments. This approach can significantly improve our understanding of molecular electronics, especially when using more complex cyclic hydrocarbons.
Ferromagnetic ordering of dopants in semiconductors has attracted considerable interest, due to their relevance for “spintronic” applications. Diamond is a wide band gap semiconductor with extreme ...properties which make it suitable for high power, high frequency and high temperature applications. Up to now mainly other semiconductors have been considered in the search for dilute magnetic semiconductors (DMS). We report
ab initio all electron, full-potential density functional theory modeling and show that the transition metal Co will order ferromagnetically when occupying a divacancy in diamond, forming a dilute magnetic semiconductor, with a magnetic moment of 0.4
μ
B per supercell, inducing two spin-polarized impurity bands in the diamond band gap. The impurity bands are shown to arise from the hybridization of the Co 3d level with diamond C 2p states.
This demonstrates that diamond may be successfully considered in the search for ferromagnetically ordered semiconductors, in particular since diamond based DMS are expected to possess high Curie temperatures, in addition to the other extreme properties of diamond.
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