Ion size is an important parameter in interpreting the electrochemical properties of the electrolyte materials. There is difficulty in selecting a representative value for ionic radius when the ion has a shape far from spherical. Since the van der Waals volume becomes a good parameter for ion size, it was calculated by numerical integral based on a simple overlapped spherical model using the optimized structures by ab initio molecular orbital calculation. We have examined the extent of errors affected by the coordinates, and given the van der Waals radii of each atom, and the integral grid size, and give the van der Waals volumes of various ions applied for the electrolyte materials of lithium batteries and double-layer capacitors. © 2002 The Electrochemical Society. All rights reserved.

The anodic stability of anions is an important factor in determining the maximum operating voltage of lithium-ion cells, if appreciable degradation is to be avoided. A linear correlation was observed between the highest occupied molecular orbital energies calculated by ab initio molecular orbital theory [HF/6-31G(d), 6­31+Gfalse(normald,normalpfalse), 6­311+Gfalse(2normald,normalpfalse)false] and the limiting oxidation potentials measured by linear sweep voltammetry, which supports experimental results that inorganic fluorine-containing anions are more resistant against oxidation than their organic counterparts: CF3SO3−

The mechanism of the photochromic cycloreversion reactions is theoretically examined in a model system of dithienylethenes by means of the CASSCF and CASPT2 methods. The structures of its conical intersections (CIs), which are the branching points of the internal conversions, were obtained. The analyses of the minimum energy paths from the Franck-Condon states and the CI points suggest that the cycloreversion reaction occurs during the intramolecular vibrational energy redistribution (IVR) toward the quasi-equilibrium on the 2A state. The current study of the model system will provide a basic insight for the photochromic molecular design.

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A theoretical study on quantum yields (QYs) of the photochromic cyclization and cycloreversion reactions is presented. It is shown that the thermodynamic relative stability of various energy minima on the ground state is primarily important for the cyclization reactions. On the other hand, the profile of the excited state potential energy surfaces (PESs) and the locations of conical intersections (CI) are important for the cycloreversion reactions. Copyright © 2007 John Wiley & Sons, Ltd.

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