Nematic order near a tricritical nematic-smectic a phase transition

A symmetric tricritical point (TCP) is demonstrated for the nematic-smectic A transition by blending two nearly identical isomers and by showing that the difference in coexistence values of the nematic order parameter S goes to zero with TCP exponent β₂ = 1 as T_TCP is approached. A horizonta λ-line is associated with an observed universal behavior of S when a new scaling of T is used.