Mixtures of two or more Lennard-Jones components are set up by changing at least one potential interaction parameter ( ε ε or σ σ ) of one of the components with respect to the other. For a binary mixture, this yields three types of pair interactions that are all modeled by the Lennard-Jones potential: 1-1, 2-2, and 1-2 interactions. For the cross interactions 1–2, additional assumptions are required for the specification of parameters ε ε 12 or σ σ 12 from ε ε 11 , σ σ 11 and ε ε 22 , σ σ 22 . Various choices (all more or less empirical and not rigorously based on physical arguments) can be used for these so-called combination rules. The most widely used combination rule is the one of Lorentz and Berthelot