Nanoscale Carbon Greatly Enhances Mobility of a Highly Viscous Ionic Liquid

Ability to encapsulate molecules is one of the outstanding features of nanotubes. The encapsulation alters physical and chemical properties of both nanotubes and guest species. The latter normally form a separate phase, exhibiting drastically different behavior compared to bulk. Ionic liquids (ILs) and apolar carbon nanotubes (CNTs) are disparate objects; nevertheless, their interaction leads to spontaneous CNT filling with ILs. Moreover, ionic diffusion of highly viscous ILs can increase 5-fold inside CNTs, approaching that of molecular liquids, even though the confined IL phase still contains exclusively ions. We exemplify these unusual effects by computer simulation on a highly hydrophilic, electrostatically structured, and immobile 1-ethyl-3-methylimidazolium chloride, [C2C1IM][Cl]. Self-diffusion constants and energetic properties provide microscopic interpretation of the observed phenomena. Governed by internal energy and entropy rather than external work, the kinetics of CNT filling is characterized in detail. The significant growth of the IL mobility induced by nanoscale carbon promises important advances in electricity storage devices

Exploding Nitromethane in silico, in real time

Nitromethane (NM) is widely applied in chemical technology as a solvent for extraction, cleaning and chemical synthesis. NM was considered safe for a long time, until a railroad tanker car exploded in 1958. We investigate detonation kinetics and reaction mechanisms in a variety of systems consisting of NM, molecular oxygen and water vapor. State-of-the-art reactive molecular dynamics allows us to simulate reactions in time-domain, as they occur in real life. High polarity of the NM molecule is shown to play an important role, driving the first exothermic step of the reaction. Presence of oxygen is important for faster oxidation, whereas its optimal concentration is in agreement with the proposed reaction mechanism. Addition of water (50 mol%) inhibits detonation; however, water does not prevent detonation entirely. The reported results provide important insights for improving applications of NM and preserving safety of industrial processes.Comment: arXiv admin note: text overlap with arXiv:1408.372

Excited States of Positronic Lithium and Beryllium

Using a variational method with an explicitly correlated Gaussian basis, we study the eþ-Li and eþ-Be complexes in the ground and lowest excited states with higher spin multiplicity. Our calculations provide rigorous theoretical confirmation that a positron can be attached to the excited states: 1s2s2p 4Po and 1s22s2p 3Po for eþ-Li and eþ-Be, respectively. The result is particularly notable for the eþ-Be complex, as the excited 3Po state lies below the autoionization threshold. We report accurate binding energies, annihilation rates and structural properties of these positron-atom systems. The existence of the ground and metastable excited states with bound positron opens up a new route to the presently lacking experimental verification of stability of a positron binding to any neutral ato