Coarse graining is commonly used in computational chemistry and physics. It is exploited in a number of classic models serving as a foundation of modern solid-state physics: tight binding , Drude-Sommerfeld's model , Hubbard's and Heisenberg's Hamiltonians. These models explain macroscopic properties of materials through effective interactions whose strengths are treated as model parameters. The values of these parameters are determined either from more sophisticated theoretical models or by fitting to experimental observables.