An Introduction covers the essentials of Computational science and explains how computational tools and techniques work to help solve nanoscale science and technological problems. The book focuses on the generalized expression of the Einstein relation composed with the different applied cases. The formulation of Einstein relation involves the countenance of electron concentration, which, in try, is determined by the energy band construction. For numerous semiconductors the electron dispersion relations are dissimilar and therefore all the succeeding formulations become adapted introducing original information. The dispersion relation for bulk materials also variations below magnetic quantization, quantum wells, quantum well wires, in inversion layers and with various types of semiconductor superlattices (SLs).