Computational Design of A New Class of Si-Based Optoelectronic Material

Computational materials science, as an intersection of theoretical physics, condensed matter physics and material science, its main tasks, in general, are firstly, research and calculate the physical and chemical properties for known materials. This would help us to better understand the microscopic mechanism of some material properties and open up new fields of applications. Secondly, computational design of new materials, that would help us to explore and design new materials to meet some proposed requirements. As we known, new material design and development is the basis of high-tech material and its device applications. The research history of computational materials science can actually be traced back to the mid 20s of last century. Immediately after the birth of quantum mechanics theory, many excellent theoretical works were applied to the study of physical properties of solid materials. In the early years of the computational materials science, it is mainly to adopt semi-empirical method. This is because the object being studied is a many-particle system which contains very large amounts of atoms and electrons. One cannot find the rigorous analytical solutions, but the empirical values of the measurable parameters are available, Therefore, in semi-empirical method, the number of experience parameters is at least as much as that of material types, hence, most studies are pointed only to the computing research category of physical properties. Until the mid 60s of last century, Hohenberg-Kohn (Hohenberg & Kohn. 1964) and Kohn-Sham (Kohn & Sham 1965) proposed the Density Functional Theory (DFT) and Local Density Approximation (LDA), to get rid of the semiempirical method restriction, and hence causing the birth of so-called ab initio or the first principles method that do not depend on experimental parameters. This method has now become a core technology of the computational material science, computational chemistry and computational condensed matter physics and is widely used. What is a First Principles for the physical world, no one seems to be specified clarify its meaning. Many physicists believe that the most precise description of atoms and smaller than the atomic system is the theory of quantum electrodynamics (QED). Therefore, QED is a theory called first principles of the micro world. In the field of condensed matter physics and materials science, within the framework of the density functional theory, if one do not consider the high-energy radiation correction, one needs only the electromagnetic theory, Schrodinger equation and/or Dirac equation and a few of parameters unrelated to specific