The maximum and effective energies of an atomic structure equal the sum of their entropic energy components. This summation is performed for systems in equilibrium entropic state and following special rules. The spatial-energy parameter is obtained, which numerically equals the most effective energy in structural interactions. The computational and analytical method for evaluating the solubility and phase formation for complex multicomponent metal systems is developed. The calculation results are quite coherent with the experimental data. The technique based on entropic principles for calculating the activation energy of self-diffusion and volumetric diffusion of atoms in solids is presented.