Dissipative particle dynamics simulations were utilized to simulate a model surfactant solution-air system. Amphiphilic surfactant molecules were modeled as dimers composed of a hydrophilic head and a hydrophobic tail. With a simple model, the influence of conservative interaction parameters on the surfactant's properties, including surfactant efficiency and critical micelle concentration (CMC), was investigated in the present research. It is not the surfactant total concentration, but the bulk concentration, that should be employed to achieve the right surfactant properties. It is found that the adjustment of interaction between water and head or air and tail (a(WH) or a(AT)) will result in the obvious change in surfactant efficiency. The parameter that affects CMC the most significantly is the interaction between water and tail (a(WT)). On the basis of the findings about the relationship between conservative interaction parameters and surfactant behaviors, we varied the interaction parameters and simulated a real ionic surfactant system with different tail lengths.
The metal atom net charge correlation (MANCC) method was developed in prediction of catalyst activity of asymmetric late-transition metal complexes, 2-quinoxalinyl-6-iminopyridine Ni (II), 2-imino-1, 10-phenanthroline Co(II) and 2-methoxycarbonyl-6-iminopyridine Pd(II) complexes, from the net charge of the metal atom for ethylene polymerization. Dreiding force field was modified according to the X-ray diffraction data. We found that the asymmetric structure of the complexes resulted in a charge difference between two halogen atoms coordinated to the metal atom. In order to remove such contribution we introduced the effective charge Q eff , which was obtained by the charge equilibration (QEq) approach. The results verified the successful introduction of Q eff and showed that the catalytic activities of different complexes are related to central metal atom effective charge. asymmetric catalyst, effective charge, force field, MANCC, QEq
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