# Difference between revisions of "F opt"

The f_opt keyword determines whether a "self-consistent sigma" calculation is performed to optimize the effective translational hard-sphere diameters of the different components (f_opt = .true., which is also the default) as presented in Ref. [1], or instead the simpler treatment of Lai et al.[2], which follows the monocomponent formalism, is used (f_opt = .false.). For the effective rotational hard-sphere diameters, see f_opt_rot.
In the original 2PT paper by Lin et al.[3], the effective hard-sphere diameter of a monocomponent system (all molecules/groups are the same) is not explicitly calculated. Instead, the fluidicity is uniquely defined from the thermodynamic state of the system, $(N,V,T)$, and the (translational) zero-frequency density of states, $S_\text{trn}(0)$.