Calculation of Molecular Orientational Order and Maxwell Displacement Current of Biaxial Molecules at the Air-liquid Interface

On the basis of the electrodynamic interaction of biaxial molecules (with their larger permanent dipoles perpendicular to the molecular axes) with a liquid surface, we calculate the molecular orientational order and the Maxwell displacement current (MDC) of biaxial molecules with a thermostatistical approach in the range of molecular area of immeasurably low surface pressure. It is shown that MDC generated by orientational change of the permanent dipoles along long molecular axes dominates the compression process shortly after the onset of the transition at A 0 from the planar surface alignment phase to the polar one, despite their smaller dipole moments than those perpendicular to the long molecular axes. This agrees with the fact that the MDC should change with the dipole moment along the long molecular axis. The results also reveal the thermodynamic motions of the dipoles parallel and perpendicular to the long molecular axis during the compression process.