However, I believe the large overview is necessary before embarking on a more stringent and detailed derivation of the mathematics. Or why Coupled Cluster inherently is an iterative method, while Perturbation Theory and Configuration Interaction inherently are non-iterative methods, although the CI problem in practice is solved by iterative techniques. In my experience, predicting structures and energetics are the main uses of computational chemistry today, although this may well change in the coming years. I have tried to include most methods which already are extensively used, together with some that I expect to become generally available in the near future. This area is outside my expertise and several excellent textbooks are already available.
Computational chemistry contains a strong practical element.
Theoretical methods must be translated into working computer programs in order to produce results. Different algorithms, however, may have different behaviors in practice, and it becomes necessary to be able to evaluate whether a certain type of calculation can be carried out with the available computers. The book thus contains some guidelines for evaluating what type of resources that are necessarily for carrying out a given calculation. I have assumed that the reader has no prior knowledge of concepts specific to computational chemistry, but has a working understanding of introductory quantum mechanics and elementary mathematics, especially linear algebra, vector, differential and integral calculus. The following features specific to chemistry are used in the present book without further introduction.