Environment, density functional theory studies

X. Jin, Y. Yan, W. Shi, S. Bi, Environ. Sci. Technol. 2011, 45, 10082-10090. Density functional theory studies on the structures and water-exchange reactions of aqueous Al(III)oxa-late complexes. 

During the last 10-20 years, a large number of efficient theoretical methods for the calculation of linear and nonlinear optical properties have been developed— this development includes semi-empirical, highly correlated ab initio, and density functional theory methods. Many of these approaches will be reviewed in later chapters of this book, and applications will be given that illustrate the merits and limitations of theoretical studies of linear and nonlinear optical processes. It will become clear that theoretical studies today can provide valuable information in Are search for materials with specific nonlinear optical properties. First, there is the possibility to screen classes of materials based on cost and time effective calculations rather then labor intensive synthesis and characterization work. Second, there is Are possibility to obtain a microscopic understanding for the performance of the material—one can investigate the role of individual transition channels, dipole moments, etc., and perform systematic model Improvements by inclusion of the environment, relativistic effects, etc. 

A good qualitative insight into the transitions involved in the color change of sensors can usually be obtained from density functional theory (DFT) and other theoretical methods that have proved to be a very accurate tool for theoretical studies in supramolecular chemistry.DFT appears to be a reasonably accurate theoretical method that is both widely available in various software packages and can be run on personal computers, that is, does not necessarily require Unix or Unix-like environments, servers, and so on. On the other hand, multireference configuration interaction methods typically offer accuracies of about 0.1 eV... 

For the calculation of properties at the atomic scale, ab initio or first-principles approaches, based on a quantum mechanical description of the interactions between electrons and atomic nuclei with the atomic numbers and masses as only input, have the advantage of a wider range of applicability with respect to e.g., different chemical environments of the atomic nuclei compared to empirical methods, at the price of higher computational complexity. The ab initio calculation of the electronic ground state structure within density functional theory [3] in the Kohn-Sham scheme [4] has become a standard approach to study bulk crystal structures, surfaces, and molecular reactions. 

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