The atomic-scale complexity presents additional challenges to computational modelling of high-entropy alloys. Thermodynamic modeling using the CALPHAD method requires extrapolating from binary and ternary systems. Most commercial thermodynamic databases are designed for, and may only be valid for, alloys consisting primarily of a single element. Thus, they require experimental verification or additional ab initio calculations such as density functional theory (DFT). However, DFT modeling of complex, random alloys has its own challenges, as the method requires defining a fixed-size cell, which can introduce non-random periodicity. This is commonly overcome using the method of "special quasirandom structures", designed to most closely approximate the radial distribution function of a random system, combined with the Vienna Ab initio Simulation Package. Using this method, it has been shown that results of a four-component equiatomic alloy begins to converge with a cell as small as 24 atoms. The exact muffin-tin orbital method with the coherent potential approximation (CPA) has also been employed to model HEAs.