HMSA

The hybrid mean spherical approximation (HMSA) smoothly interpolates between the HNC and the mean spherical approximation closures

$g(r)=\exp (-\beta u_r(r))(1+\frac{\exp [f(r)(h(r)-c(r)-\beta u_a(r))]-1}{f(r)})$

where $g(r)$ is the radial distribution function.