Vapor-liquid equilibrium calculations require global minimization of deviations in pressure and gas phase compositions. In this work, two versions of a stochastic global optimization technique, the genetic algorithm, the freeware MyGA program, and the modified mMyGA program, are evaluated and compared for vapor-liquid equilibrium problems. Reliable experimental data from the literature on vapor liquid equilibrium for water + formic acid, tert-butanol + 1-butanol and water + 1,2-ethanediol systems were correlated using the Wilson equation for activity coefficients, considering acid association in both liquid and vapor phases. The results show that the modified mMyGA is generally more accurate and reliable than the original MyGA. Next, the mMyGA program is applied to the CO2 + ethanol and CO2 + 1-n-butyl-3-methylimidazolium hexafluorophosphate systems, and the results show a good fit for the data.

We present a theoretical investigation on the properties of interstitial nickel and its related complexes in diamond. The atomic configurations, symmetries, spins, and energetics of interstitial nickel, nickel-boron and nickel-vacancy complexes were investigated by a total energy ab initio methodology. Those results are used to explain certain electrically active centers, commonly found in synthetic diamond.

Isolated nickel impurities in diamond have been investigated using the spin-polarized full-potential linearized augmented plane wave total energy method. The electronic and atomic structures, symmetries, transition energies, and formation energies of substitutional and interstitial Ni impurities in diamond were computed. The results were discussed in the context of the electrically active centers in synthetic diamond.