Screening enhancement factors for four major reactant pairs as a function of density at kT = 150 keV and Y_e = 0.5. The density at which all SEFs are equal is temperature dependent. (Top left:¹²C+α, top right:¹⁶O+α, bottom left:¹²C+¹²C, bottom right:¹⁶O+¹⁶O.) Solid lines indicate classical screening; red, dashed lines indicate relativistic screening; and blue, dotted lines indicate the relativistic approximation.