TABLE OF CONTENTS For over 10 years a large amount of work worldwide has been directed towards obtaining an understanding of the new covalently bonded nanomaterials made from light atomic weight elements from the first row of the periodic table because of the novel microstructures and the extraordinary combination of physical properties (Wang, 1997, 1999; Veprek, 1999). For example, Cohen proposed that carbon nitride should have diamond-like properties with a relatively isotropic arrangement of short ( 0.147 nm in length) and covalent ( 7% ionic) bonds (Cohen, 1985, 1989a, 1989b). Such materials with high hardness and toughness, oxidation resistance, chemical stability, high adherence, and high thermal conductivity, are important in high-performance engineering applications for high-temperature, high-power, or high-frequency devices ranging from microelectronic to spaceflight industries.
In addition to the potential applications, the goal of this effort is also to see if one can design a high-performance material by beginning with theories to select candidates for laboratory synthesis. As one of the computer designed structures, this study provides a test of the effectiveness of first-principles calculations in materials science. It is the purpose of the present chapter to survey the recent work which has been carried out and to detail the level of understanding which has been attained in the research of light-element nanomaterials.
A number of workers have published theoretical calculations for light-element compounds, for example of carbon nitride polymorphs. An early empirical model (Cohen, 1985) is directed towards understanding their covalent...
