The major goals of quantum chemistry include increasing the accuracy of the results for small molecular systems and increasing the size of large molecules that can be processed, which is limited by scaling considerations?the computation time increases as a power of the number of atoms. This book offers scope for academics, researchers, and engineering professionals to present their research and development works that have potential for applications in several disciplines of computational chemistry. Contributions range from new methods to novel applications of existing methods to gain an understanding of the concepts.