Confining CO2 inside the nanocavities of the sI clathrate: a quantum dynamics study

ICPEAC 2015, Toledo, Spain on 22 –28 July 2015; http://www.icpeac2015.com/Clathrate hydrates have been found to occur naturally, and have been extensively studied due to their important industrial applications, such as the storage of the CO2 from the atmosphere and control climate change. Thus, quantitative understanding of physical and chemical properties, as well as the factors that control the formation of CO2 hydrates, on both macroscopic and microscopic levels is essential in several areas of physical science.Peer Reviewe

Modeling the water-halide ion interactions

1 pág.; 1 fig.; XXIX International Conference on Photonic, Electronic, and Atomic Collisions (ICPEAC2015); Open Access funded by Creative Commons Atribution Licence 3.0Ions play an important role in many heterogeneous processes, and understanding specific ion effects is a key point in studying solvation mechanisms in liquids as well as reactivity of aerosol particles. In this regard, a crucial issue to be resolved is the extent to which ions influence the structural and dynamical properties of the surrounding hydrogen bond network and, at the same time, to provide a direct molecular-level interpretation of the experimental measurements.Peer Reviewe

Structural changes in water and Ar-water clusters under high pressure

1 pág.; 1 fig.; XXIX International Conference on Photonic, Electronic, and Atomic Collisions (ICPEAC2015); Open Access funded by Creative Commons Atribution Licence 3.0Specific size gas-water clusters are currently receiving considerable attention, as models for inclusion compounds of different type of clathrate hydrates. As model microsolutions they retain many characteristics of the bulk, are theoretically tractable, and can be used to probe the relevant guest/host interactions, as well as to derive and to test intermolecular potentials that can be also used under different thermodynamic conditions.Peer Reviewe

Deformability and solvent penetration in soft nanoparticles at liquid-liquid interfaces

arXiv:1911.06725v1[Hypothesis]: The internal topology of soft nanoparticles – regular (ideal) vs disordered (realistic) networks – and its intrinsic deformability (degree of cross-linking) influences solvent permeability (uptake, invasive and mixing capacities) under interfacial confinement.[Methodology]: By means of large-scale molecular dynamics simulations we study nanogels at liquid-liquid (A-B) interfaces covering the whole range of cross-linking degrees and interfacial strengths. The nanogel permeability is analyzed with a grid representation that accounts for the surface fluctuations and adds to the density profiles the exact number of liquid particles inside the nanogel. Unlike in previous investigations, excluded volume interactions are considered for all the particles (monomers and liquids).[Findings]: Nanogel’s permeability is intrinsically related to the particle deformability. Ideal networks show higher values of the total liquid uptake and the invasive capacity (A-particles in B-side and vice versa) than realistic networks, though differences vanish in the limit of rigid interfaces. Uptake and invasion are optimized at a cross-linking degree that depends on the interfacial strength, tending to % for moderate and stiff interfaces. As the interfacial strength increases, the miscibility inside the nanogel is enhanced by a factor of up to 5 with respect to the bare interface, with the disordered networks providing a better mixing than their ideal counterparts.DJAA acknowledges the career funding support from the DIPC foundation. This work has been supported by the projects PGC2018-094548-B-I00 (MCIU/AEI/FEDER, UE) and IT-1175-19 (Basque Government, Spain).Peer reviewe

Coarsening kinetics of complex macromolecular architectures in bad solvent

This article belongs to the Section Polymer Physics.This study reports a general scenario for the out-of-equilibrium features of collapsing polymeric architectures. We use molecular dynamics simulations to characterize the coarsening kinetics, in bad solvent, for several macromolecular systems with an increasing degree of structural complexity. In particular, we focus on: flexible and semiflexible polymer chains, star polymers with 3 and 12 arms, and microgels with both ordered and disordered networks. Starting from a powerful analogy with critical phenomena, we construct a density field representation that removes fast fluctuations and provides a consistent characterization of the domain growth. Our results indicate that the coarsening kinetics presents a scaling behaviour that is independent of the solvent quality parameter, in analogy to the time–temperature superposition principle. Interestingly, the domain growth in time follows a power-law behaviour that is approximately independent of the architecture for all the flexible systems; while it is steeper for the semiflexible chains. Nevertheless, the fractal nature of the dense regions emerging during the collapse exhibits the same scaling behaviour for all the macromolecules. This suggests that the faster growing length scale in the semiflexible chains originates just from a faster mass diffusion along the chain contour, induced by the local stiffness. The decay of the dynamic correlations displays scaling behavior with the growing length scale of the system, which is a characteristic signature in coarsening phenomena.This research was funded by projects PGC2018-094548-B-I00 (MCIU/AEI/FEDER, UE) and IT-1175-19 (GV, Spain).Peer reviewe

Density-functional approximations on CO2@sI clathrate hydrate interactions

1 pag., 1 fig. -- Open Access funded by Creative Commons Atribution Licence 3.0Clathrate hydrates have unique physical and chemical properties and considering that the stability of such systems is strongly related with its guest. In the last decades a renewed interest on these substances have grown up due to their potential industrial applications, with gas hydrate research becoming a joint field of various engineering disciplines and fundamental sciences.Peer Reviewe

Solid-like transitions in rare-gas water clusters

7th International Meeting on Atomic and Molecular Physics and Chemistry, Le Havre, Normandy, June 27-30, 2016 ; https://imampc2016.sciencesconf.org/Peer Reviewe

Density-functional approximations on CO2@sI clathrate hydrate interactions

1 pag., 1 fig. -- Open Access funded by Creative Commons Atribution Licence 3.0Clathrate hydrates have unique physical and chemical properties and considering that the stability of such systems is strongly related with its guest. In the last decades a renewed interest on these substances have grown up due to their potential industrial applications, with gas hydrate research becoming a joint field of various engineering disciplines and fundamental sciences.Peer Reviewe

Quantum dynamics of carbon dioxide encapsulated in the cages of the si clathrate hydrate: Structural guest distributions and cage occupation

12 págs.; 7 figs.; 6 tabs.© 2015 American Chemical Society. We perform quantum multiconfiguration time-dependent Hartree calculations for the two cages of the sI CO2 clathrate hydrate, and we report, for first time, results on the translational, rotational, and vibrational states. The potential surface is constructed by the semiempirical SPC/E water model and pairwise additive interactions between the CO2 molecule and all water molecules forming each cage, while a spectroscopic-determined potential is used for the CO2 monomer. The exact kinetic energy operator is derived for the linear CO2 in the cage, and the potential energy operator is adapted to combined mode schemes, chosen adequately in order to obtain the desired product representation. The rotational ability of the CO2 is hindered in the small cavities (512), while in the large cage (51262) translational and rotational degrees of freedom are highly coupled. By analyzing the corresponding T-R eigenstates, we established a connection with experimental X-ray measurements on the orientation of the CO2 molecule in the two cages. Further, vibrational excitations of the fundamental symmetric and antisymmetric stretch modes, their overtones, and combination bands are computed from 7D quantum calculations. We found significant frequency shifts, which are comparable to those observed in the double-peak profile of the experimentally recorded infrared spectra, for the CO2 molecule trapped in the small and large cages of the sI clathrate hydrate. Such good agreement, with the data from recent spectroscopic studies of carbon dioxide clathrate hydrate at low temperatures, indicates a single occupancy of the sI structure cages, allowing an assessment of the theoretical approaches employed.The authors thank the Centro de Calculo (IFF), SGAI (CSIC), and CESGA for allocation of computer time. A.V. acknowledges financial support from Vicerrectoria de investigación at ́ Universidad de Antioquia (CODI Project E01538 and Estrategia de Sostenibilidad 2013−2014). This work has been supported by MICINN Grant FIS2011-29596-C02-01 and COST Actions CM1002 (CODECS) and CM1204 (XLIC).Peer Reviewe