Quantum chemical methods have been used to study reduction mechanisms of ethylene carbonate ͑EC͒, propylene carbonate ͑PC͒, and vinylethylene carbonate ͑VEC͒, in electrolyte solutions. The feasibility of direct two-electron reduction of these species was assessed, and no barrier to reaction was found for the formation of Li 2 CO 3 and 1,4-butadiene from VEC. In contrast EC and PC have barriers to reaction on the order of 0.5 eV. The ready formation of Li 2 CO 3 when VEC is reduced may explain why it acts as a good passivating agent in lithium-ion cells.

We present an embedded cluster approach for modeling interactions in zeolites and an application of this model to the study of NH 3 and NH 4 + adsorption in chabazite. This model utilizes the SCREEP (surface charge representation of the electrostatic embedding potential) formalism to include an accurate description of the Madelung potential in quantum mechanical calculations. The model is validated by comparison with previous cluster, embedded cluster, and periodic calculations on this system. The importance of including the Madelung potential and geometry relaxation in zeolite calculations is addressed. After considering the effects of electron correlation, basis set superposition error, and the zero-point energy, the model yields a heat of adsorption of -170 kJ/mol for NH 4 + in chabazite, in good agreement with experimental TPD data.

The structures and dissociation energies of Li n ·(C6H6) n +1 sandwich complexes (n = 1−6) have been investigated using quantum chemical techniques. At the G3(MP2) level of theory, the Li·(C6H6)2 complex exhibits a Jahn−Teller distortion, forming a D 2 h charge-separated species [C6H6 -1/2−Li+−C6H6 -1/2] with a surprisingly large dissociation energy of 0.85 eV, and a short benzene−benzene distance of 3.54 Å. Comparisons are made with the Li·C6H6, Li+·C6H6, and Li+·(C6H6)2 complexes. The larger (n > 1) complexes were studied at the B3LYP/6-31G(d) level and were also found to have large dissociation energies, ca. 0.85 eV per Li atom, and short benzene−benzene distances (3.70 Å).

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Computational materials science based on ab initio calculations has become an important partner to experiment. This is demonstrated here for the effect of impurities and alloying elements on the strength of a Zr twist grain boundary, the dissociative adsorption and diffusion of iodine on a zirconium surface, the diffusion of oxygen atoms in a Ni twist grain boundary and in bulk Ni, and the dependence of the work function of a TiN-HfO(2) junction on the replacement of N by O atoms. In all of these cases, computations provide atomic-scale understanding as well as quantitative materials property data of value to industrial research and development. There are two key challenges in applying ab initio calculations, namely a higher accuracy in the electronic energy and the efficient exploration of large parts of the configurational space. While progress in these areas is fueled by advances in computer hardware, innovative theoretical concepts combined with systematic large-scale computations will be needed to realize the full potential of ab initio calculations for industrial applications.