For a three-dimensional Fermi gas (noninteracting electron gas), the screening wavevector k 0 can be expressed as a function of both temperature and Fermi energy E F . The first step is calculating the internal chemical potential μ μ , which involves the inverse of a Fermi–Dirac integral, μ μ k B T = F 1 / 2 − − 1 [ 2 3 Γ Γ ( 3 / 2 ) ( E F T ) 3 / 2 ] .