ABSTRACT
Recent advances in computational methods as well as quickly growing performance of computers resulted in the burst of application of computational chemistry tools to study catalysts and catalytic reactions. Most of the examples of application of the modern quantum chemistry methods are based on density functional theory (DFT). The details of the mathematical formulation of the DFT an interested reader may ‚nd in a specialized literature. The selection of this formalism is usually due to the fact that it combines high accuracy with relatively low cost of calculations, which is of utmost importance taking into account the usual complexity of the studied catalytic systems. DFT is based on the theorem formulated by Hohenberg and Kohn in 1964, which states that all ground state properties of a system are uniquely determined by its electron density ρ. This approach allows for the simpli‚cation of the calculations in comparison to the classical quantum mechanics,whichoperatesinthevirtualspaceof4Ndimensional(whereNdenotes the number of electrons); DFT deals with an observable ρ, which can be accessed by experiment (x-ray diffraction measurements), and is a function in the real 3D space. Accordingly, DFT allows for the study of the larger systems than traditional quantum mechanical methods. Another important factor explaining the increasing popularity of the DFT method is the inclusion of the electron correlation, rendering it particularly suited for the description of systems containing transition metals, which often play the role in the catalysts.
