where V lm is the excluded volume, i.e. the volume taken up by particle of type l in which particles m cannot be found. This volume is nontrivial to obtain exactly, but as a first-order approximation, we assume it to be spherical V lm = (4/3)πR 3 lm , with a radius R lm that has to be estimated either by inspection of the RDFs or by fitting (vide infra). Note that V lm is the volume inaccessible to the remaining particles, and not just the total volume divided by the total number of particles (which would be larger than V lm , c.f. close-packing of equal spheres only uses 74% of the total volume).