From Bulk to Nano Understanding the Transition through Computer Simulations

JIMENA A. OLMOS ASAR

Nanostructured Multifunctional Materials

Taylor & Francis

Año: 2021; p. 261 - 273

When going from the infinite bulk to the nano regime, one finds that several properties of the material change. A large surface/volume ratio appears, increasing as the size of the system decreases, and with it, a higher density of low-coordinated atoms on the surface become potential reactive sites. Furthermore, electronic confinement starts to play an important role in the material?s behaviour. These changes, among other novel properties, give the nanomaterial unique characteristics that usually differ significantly from those of their bulk counterpart. Despite the incredible progress of the experimental techniques in the last decades, an atomistic description of these complex nanoscale systems remains a big challenge. The recent development of new theoretical methodologies, numerical techniques and software, together with the ever-increasing computational power, has been responsible for the rise of computer simulations, a powerful and reliable tool that provides an in-depth atomic/electronic description of systems, from bulk to nanostructures and surfaces.Computer simulations can be described as a set of techniques associated with the use of a computer to simulate a system with a program or code. It involves a mathematical model composed by equations, which try to mimic the real system, and the results are obtained in the form of data to be later interpreted. The ?experiments? are performed inside a computer, and for this reason, there is no limit in treating dangerous or expensive systems. Moreover, materials which have not been yet synthesized can be idealized in the computer. The possibility to replicate real-world events allows researchers in all types of academic disciplines and commercial industries to figure out how things would function or act in certain environments without having to physically replicate those conditions.Once a level of theory is chosen, according to the system to simulate and the expected results, the main limitation of a simulation is the computational capabilities. In the last few years, with the appearance and development of high-performance supercomputers, larger systems could be handled. On the other hand, the enhancement of resolution in experimental techniques allows scientists to measure matter at really low size levels (even individual atoms). The combination of these capabilities gets the experimental and theoretical studies to the same size level, so the results can be directly compared, and a global study of a material can be reached.In this chapter, the predictive power of computer simulations is discussed, evolving from merely descriptive tools to methodologies that have revolutionized the research in the development of new materials. Different levels of theory and computational tools to characterize a material are also briefly described. Finally, some properties, which are characteristic of low dimensional materials, are presented.