Ab initio investigation of the affinity of novel bipyrazolate-based MOFs towards H2and CO2

Two recently synthesized Zn and Cu tetramethyl-bipyrazole-based metal organic frameworks have been characterized and compared as regards their structural and electronic properties and their reactivity towards hydrogen and CO2 molecules. Ab initio calculations have been performed on periodic models with the B3LYP hybrid and an empirical long-range dispersion correction. Interactions with the probe molecules in the two structures are almost iso-energetic and in all cases the physisorption becomes reversible as the temperature increases. Topological analysis of the electron density has been used to fully characterize the chemical bonding. On the basis of our study, it can be inferred that the experimentally observed larger adsorption capacity of the Cu framework is not ascribable to the strong interaction of the guest molecules with an exposed metal ion but to the higher number of adsorption sites and to the larger void volume

In Ricordo di Ettore Gelpi(II Hommage a Ettore Gelpi, Part 1 Memorial Articles for Ettore Gelpi)

この論文は国立情報学研究所の学術雑誌公開支援事業により電子化されました

Understanding the fluidity of condensed phase systems in terms of voidsnovel algorithm, implementation and application

Solvation processes, transport properties, and fluidity of condensed phases can be described considering the void space between the particles of the system. In this work a novel algorithm for the analysis of this void in molecular dynamics simulations is presented. Based on suitable void spheres which are fitted between the atoms a void domain is defined employing a Voronoi tessellation scheme. The algorithm is not only providing the distribution of the void sphere's radii, but also contains extensions to analyses details of the static structure and the dynamical behavior of the void space. The first extension is realized by recalculating the void domain neglecting void spheres of a certain size, the second by calculating autocorrelation functions of the probability to find certain grid-based points as part of the void domains. Furthermore, the performance of the new analyses is demonstrated on two suitable case studies. Thereby, the proper functionality of the new algorithm is shown by comparing the void radii distribution obtained by the new algorithm to results from the literature. The further analyses applying the extensions show a crucial influence of the density during the simulation, especially on the dynamical behavior

Tuning Solvent Miscibility: A Fundamental Assessment on the Example of Induced Methanol/n-Dodecane Phase Separation

In this work, we assess the fundamental aspects of mutual miscibility of solvents by studying the mixing of two potential candidates, methanol and n-dodecane, for nonaqueous solvent extraction. To do so, H-1 NMR spectroscopy and molecular dynamics simulations are used jointly. The NMR spectra show that good phase separation can be obtained by adding LiCl and that the addition of a popular extractant (tri-n-butyl phosphate) yields the opposite effect. It is also demonstrated that in a specific case the poor phase separation is not due to the migration of n-dodecane into the more polar phase, but due to the transfer of the extractant into it, which is especially relevant when considering industrial applications of solvent extraction. With the aid of molecular dynamics simulations, explanations of this behavior are given. Specifically, an increase of all hydrogen-bond lifetimes is found to be consequent to the addition of LiCl which implies an indirect influence on the methanol liquid structure, by favoring a stronger hydrogen-bond network. Therefore, we found that better phase separation is not directly due to the presence of LiCl, but due to the "hardening" of the hydrogen-bond network

Tuning Solvent Miscibility: A Fundamental Assessment on the Example of Induced Methanol/n-Dodecane Phase Separation

In this work, we assess the fundamental aspects of mutual miscibility of solvents by studying the mixing of two potential candidates, methanol and n-dodecane, for nonaqueous solvent extraction. To do so, 1H NMR spectroscopy and molecular dynamics simulations are used jointly. The NMR spectra show that good phase separation can be obtained by adding LiCl and that the addition of a popular extractant (tri- n-butyl phosphate) yields the opposite effect. It is also demonstrated that in a specific case the poor phase separation is not due to the migration of n-dodecane into the more polar phase, but due to the transfer of the extractant into it, which is especially relevant when considering industrial applications of solvent extraction. With the aid of molecular dynamics simulations, explanations of this behavior are given. Specifically, an increase of all hydrogen-bond lifetimes is found to be consequent to the addition of LiCl which implies an indirect influence on the methanol liquid structure, by favoring a stronger hydrogen-bond network. Therefore, we found that better phase separation is not directly due to the presence of LiCl, but due to the "hardening" of the hydrogen-bond network.status: publishe

Unraveling the nano-structure of a glassy CaO-FeO-SiO2 slag by molecular dynamics simulations

status: publishe

Media, esperienza e racconto biografico. La comunicazione multiculturale: quattro comunit\ue0 di immigrati a Milano

L'articolo rende conto della ricerca qualitativa sull'uso dei media da parte dei membri di quattro comunit\ue0 di stranieri migrati a Milano; particolare attenzione \ue8 posta sulla dimensione narrativa del racconto biografico sollecitata dal consumo medial

Hydrophilic Ionic Liquid Mixtures of Weakly and Strongly Coordinating Anions with and without Water

With the aid of ab initio molecular dynamics simulations, we investigate an ionic liquid (IL) mixture composed of three components 1-butyl-3-methylimidazolium [C₄C₁Im]⁺, tetrafluoroborate [BF₄]⁻, and chloride [Cl]⁻ without and with water. In the pure IL mixture, we observe an already complex network of interactions between cations and anions, and addition of water to the system even extends the complexity. Observed number integrals show that the coordination number between cations and anions is reduced in the system with water compared to that in the pure system. Further studies show that the Coulombic network of the strongly coordinating anion [Cl]⁻ is disturbed by water, while that of the weakly coordinating anion [BF₄]⁻ is not. These observations can also be confirmed by the Voronoi polyhedra analysis, which shows that the polar network of microheterogeneous IL collapses by the introduction of water. Hydrogen-acceptor interactions revealed that the [Cl]⁻ anions are transferred from being situated in the IL to the water continuum, while [BF₄]⁻ is almost unperturbed; these effects mainly influence the interplay of the ionic liquid network