Dimensionless Wigner-Seitz radius ($r_s$)

Write $(3/(4\pi n){)}^{1/3}=r_s{a}_B^{\ast }$, where $a_B^{\ast }=4\pi \epsilon {\hslash }^2/(m^{\ast }{e}^2)$. Here $r_s$ is dimensionless, unlike a Wigner-Seitz radius measured as a length. Electron-gas energy formulas quoted in effective atomic units commonly use this convention.