Activity coefficients at infinite dilution γ i ∞ of 19 alkanes, alkenes, and alkylbenzenes in the ionic liquid 4-methyl-n-butylpyridinium tetrafluoroborate (C 10 H 16 BF 4 N) were determined by gas chromatography using the ionic liquid as stationary phase. The measurements were carried out at different temperatures between 313.1 K and 363.1 K. From the temperature dependence of the limiting activity coefficients partial molar excess enthalpies at infinite dilution H i E,∞ of the organic solutes in the ionic liquids have been derived.

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The standard molar enthalpies of vaporization ∆ l g H°m of the 14 branched C 5 and C 6 alkanols 2,2dimethyl-1-propanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, 2-ethyl-1-butanol, 3,3-dimethyl-1-butanol, 2-hexanol, 3-hexanol, 3-methyl-2-pentanol, 4-methyl-2-pentanol, 2-methyl-3-pentanol, 3,3-dimethyl-2butanol, 2-methyl-2-butanol, 3-methyl-3-pentanol, and 2,3-dimethyl-2-butanol have been determined. The data were obtained from the temperature dependence of the vapor pressure measured by the transpiration method. A linear correlation of enthalpies of vaporization of the secondary alcohols with the number of C atoms has been found. The effect of self-association of aliphatic alcohols in the liquid phase is discussed in terms of the difference of ∆ l g H°m(298.15 K) between associating alcohols and their nonassociating alkane homomorphs.

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In this contribution, several vacancy-solute complexes in iron are investigated theoretically from the viewpoint of positron annihilation. In particular, V-Si, V-P, V-Cr, V-Mn, V-Ni, V-Cu and V-Mo complexes are examined. In addition, nano-sized vacancy-Cu clusters in the Fe matrix are also studied. We concentrate on positron lifetimes and coincidence Doppler broadening profiles that bring complementary information about the studied complexes and their clusters. Positron calculations are carried out using the atomic superposition method employing realistic atomic configurations obtained recently using an ab initio pseudopotential method (vacancy-solute complexes) and Monte Carlo/molecular dynamics methods (vacancy-Cu clusters). The main aim of this study is to predict as to what extent such defects are detectable and differentiable using positron annihilation techniques. The results obtained are discussed in the context of experimental data available in the literature. #

The evolution of argon-filled nanocavities in a copper crystal under annealing is studied experimentally and theoretically. The subsurface argon-filled nanocavities are formed after a short annealing at a temperature ∼1000 K by coalescence of subsurface defects initially created by argon implantation. The further prolonged annealing at a temperature above 1075 K leads to decomposition of the nanocavities and diffusion of implanted argon out of the sample. According to a simple analysis, the mechanism of the nanocavity formation is governed not only by the migration of simplest defects, such as vacancies and argon and copper interstitials, but also to a large extent, by diffusion and interaction of the complexes of these simplest defects. The experimental studies with x-ray photoelectron spectroscopy and scanning tunneling microscopy and spectroscopy provide valuable data sets of the density of nanocavities and their size and depth distribution. Based on the experimental results, a theoretical model is developed. The calculation with the model proves that the growth of the nanocavities is mainly determined by the temperature-induced migration of vacancy-argon complexes. By combining the experimental data with the simulation results, the migration energy of these kinds of complexes is estimated ∼2.55-2.75 eV. Moreover, the calculation with our model provides the estimate of the dissociation energy of a multiple complex, consisting of two vacancies and two argon atoms, as 1.10-1.18 eV. These parameters, reported in this article, play a key role in the description of the kinetics of the growth and decomposition of nanocavities.

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