Edge dislocation in a vertical smectic-A film: line tension versus temperature and film thickness near the nematic phase

The line tension of a dislocation is measured in a vertical smectic-A film as a function of temperature and film thickness. There are two contributions to the line tension: a bulk contribution that corresponds to the energy of the dislocation in an infinite medium and a surface correction that accounts for interactions with the two free surfaces. Both terms are measured in pure 8CB (octylcyanobiphenyl) as a function of temperature when the bulk nematic-smectic-A transition temperature T(c) is approached.