Ferroelectric states of a dipolar fluid confined to a slit-pore

Monte-Carlo simulation results are reported for a strongly coupled dipolar soft-sphere (DSS) fluid confined by two planar, non-conducting walls with wall separation L-2=7sigma (sigma being the diameter of the spheres). Simulations are performed in an isothermal-isobaric ensemble where the pressure parallel to the walls is fixed. Choosing appropriate values for temperature and dipole moment we demonstrate that the confined system, when compressed towards high parallel pressures, develops spontaneous polarization (i.e. ferroelectric behavior) similar to what is seen in bulk DSS fluids. In the pressure range investigated the ferroelectric states of the confined system are liquid-like in directions parallel to the walls, but stratified in z-direction. A further confinement- induced effect, which can be understood via energetic arguments, is that the global director (d) over cap characterizing the ferroelectric order points in a direction parallel to the walls. Due to this restriction the isotropic-to-ferroelectric transition occurs at significantly lower pressures/densities than in the bulk where the direction of (d) over cap is unrestricted. (C) 2003 Elsevier B.V. All rights reserved.