To study the behavior of diffusion coefficients near the critical point of argon-krypton mixtures, molecular dynamics simulations were performed. Two-dimensional Lennard-Jones molecular simulation was employed to reduce the effect of periodic boundary conditions near the critical point.Simulation showed a qualitative decrease in the diffusion coefficients and strong composition dependence near the critical point, as experimentally observed for carbon dioxide-benzene and carbon dioxide-acetone systems using the Taylor dispersion technique.
We have been performing the analysis of organic reactions using MOPAC in order to evaluate its usefulness. On the course of the study, two stable structures with different length of MgCl bond for Grignard reagents, CH3MgCl, were obtained by MNDO-PM3. AM1, PM3 and MNDO-d Hamiltonians in MOPAC were used for the evaluation of another metal halides, MXn, comparing with experimental and ab initio calculation results. PM3 calculation results showed two stable structures with different M-X bond length for several metal halides.
The addition reactions of CH3, CH2F, CHF2 and CF3 radicals to ethylene, monofluoroethylene, difluoroethylene, trifluoroethylene and tetrafluoroethylene have been investigated by using density functional theory (DFT) and Hartree-Fock (HF) methods. In the DFT calculations we have used both pure and hybrid (partly including HF) exchange and Lee/Yang/Parr or Perdew/Wang 91 correlation functionals with the 6-31 G* basis set. The same basis was taken in the HF calculations. For all possible combinations of fluorosubstituted methyl radicals and ethylenes, the structures of reactants and transition states have been located. Inclusion of electron correlation was shown important in reproducing experimental activation barriers. In addition, the results were strongly dependent on the type of functionals. The Becke's three-parameter hybrid with Perdew/Wang 91 gradient-corrected correlation functional B3PW91 gave the best estimates of the activation energies.
Vibrational frequencies and infrared intensities of dichloromethane CH2Cl2 molecule in the gas phase have been calculated with the ab initio molecular orbital method using many combinations of basis set functions and electron correlation correction methods, and compared with experimental values. Dependence of calculated frequencies and intensities on basis set function and electron correlation correction method was made clear, and a recommended combination of basis set function and electron correlation correction method was proposed.