DAC-investigations on the phase behaviour of liquid crystals up to 16 KBAR and 550 k using a nearly noniterative method of deconvoluting the ruby doublet in pressure determination

Abstract

In a diamond anvil cell mounted in a polarizing microscope mesophase transitions are observed optically. Phase transition pressures at high temperatures are determined with increased accuracy by deconvoluting the ruby fluorescence doublet. A special linearization of the model line shape (a sum of two modified Lorentzians) is used. The distance between the two separated peaks does not change up to 570 K, the parameters are consistent in the entire temperature range. The method is applied at high temperatures and “low” pressures, which is a problematic range for DAC-studies. The T(p) phase diagram of trans-4-n-propyl (4-n-butoxyphenyl) cyclohexane (PCH3O4) up to 16 kbar is presented showing a pressure induced smectic B phase. The stability of the mesophases is discussed.

Key Words:

• PCH3O4
• liquid crystalline phases
• pressure induced smectic B phase
• diamond anvil cell
• ruby fluorescence method
• stability of mesophases