function DiffusivityEffCoeff input Types.Temperature T ""; input Types.Pressure p ""; input Integer species1 ""; input Integer species2 ""; input Types.Length collDiam ""; input Types.CollisionIntegral collIntegral ""; input Real ratioPorTor ""; output Types.DiffusionCoefficient Deff_1_2 ""; end DiffusivityEffCoeff;