Atomistic simulations of elementary steps of important surface reaction processes based on heterogeneous metallic catalysis represent a rational background for the design of new and improved catalysts. We have studied by means of density functional theory calculations, the interaction of oxygen, carbon monoxide, hydrocarbons, and nitrogen oxides with transition metal surfaces, which are adsorbates involved in catalytic reactions important to reduce the emission of undesirable exhaust gases. Development of XCRYSDEN graphical package has filled an inportant gap in the practical, daily-use aspect of condensed-matter atomistic simulations. Namely, crystal structure is a very important input for any electronic structure calculation, and virtually the only reasonable check of the structure is by means of visualization. XCRYSDEN was one among the first non-comercial packages, devoted to visualization of crystal structures and properties such as charge densities, band structures, and Fermi surfaces. a) we expect that the procedures developed and tested in our study will be implemented in applied research on active fauls and earth avalancheS