ABSTRACT
Carbon nanomaterials consisting of graphenes, nanotubes and fullerenes are the hi-tech and the smartest materials of the present era. Elemental carbon in the sp2 hybridization can form a variety of amazing structures. Apart from the wellknown graphite, carbon can build an infinite number zero dimensional closed cages consisting entirely of carbon, which are called fullerenes. Besides this, carbon can also form different one-dimensional (1D) crystalline geometries in the form of seamless cylinders known as nanotubes. The discovery of fullerenes and carbon nanotubes has aroused remarkable excitement not only in experimental chemistry but also in computational chemistry. A lack of experimental knowledge about the electronic processes in nano-systems has expedited the progress in computational chemistry. In recent years, many computational studies have been performed on nano-systems for their mechanical and electrical properties including their conductivity, superconductivity, ferromagnetism, charge transport, optical and nonlinear optical properties. Of particular interest to the present work are their strong electrical and nonlinear optical properties, as measured by several quantum chemical methods. Nano-systems have been potential candidates for nonlinear application because of their extensive π-conjugation. Fullerenes and carbon nanotubes have been challenging molecules for first-principles calculations because of their relatively larger sizes. Recent advances in parallel and supercomputing have brought a substantial improvement in capabilities of quantum chemical methods for predicting the optical and nonlinear optical properties of large molecules like fullerenes and carbon nanotubes. Quantum chemical methods are becoming more important and more practical for the interpretation of structure property relationships at molecular level. Computations have been performed on these nano-systems to functionalize them by either covalent attachment of chemical groups or the noncovalent adsorption or wrapping of various functional molecules. The role of several functionalized nano-systems to modify the electrical and optical properties in the field of carbon nanomaterial will be reviewed in this chapter, in which an overview of different structure property relationships applied to assess the electrical and nonlinear optical properties will be summarized.
