A Dissipative-Particle-Dynamics Model for Simulating Dynamics of Charged Colloid

A mesoscopic colloid model is developed in which a spherical colloid is represented by many interacting sites on its surface. The hydrodynamic interactions with thermal fluctuations are taken accounts in full using Dissipative Particle Dynamics, and the electrostatic interactions are simulated using Particle-Particle-Particle Mesh method. This new model is applied to investigate the electrophoretic mobility of a charged colloid under an external electric field, and the influence of salt concentration and colloid charge are systematically studied. The simulation results show good agreement with predictions from the electrokinetic theory.Comment: 17 pages, 8 figures, submitted to the proceedings of High Performance Computing in Science & Engineering '1

Mechanism in Organic Chemistry

x;ill.;378hal.;24c

Mechanism in Organic Chemistry

x;ill.;378hal.;24c

Molecular structure of 3,3-diethylpentane (tetraethylmethane) in the gas phase as determined by electron diffraction and ab initio calculations

The molecular structure of 3,3-diethylpentane (tetraethylmethane) in the gas phase has been determined by electron diffraction and ab initio calculations at the MP2/6-31G* level. Five local minima on the potential energy surface were located, but only two have significant populations at room temperature. The experimental distribution of conformers was found to be 66(2)% with D(2d) symmetry and 34(2)% with S symmetry, corresponding to an energy difference ΔH°in favor of the D(2d) form of 3.3(2) kJ mol. The molecule shows significant distortion from regular tetrahedral coordination at the central carbon atom, with two CCC angles in the D(2d) form reduced to 106.7(8)°and two angles in the S form increased to 110.9(4)°. These distortions are attributed to asymmetry of the electron density distribution around the CH groups