Dipolar interactions in model Langmuir–Blodgett films

Abstract

Planewise dipole sums give the electric field at a point due to an array of electric dipole moments in a plane. Calculations are reported for model lattice structures of Langmuir–Blodgett films with elongated molecules represented by a string of spherical ‘‘beads’’ or submolecules; interactions are averaged over submolecules. Results are given for parent hexagonal and tetragonal lattices, with molecules allowed to tilt away from the vertical and with the in‐layer cell parameters allowed to distort from equality. Beyond about five submolecules, molecular length makes little difference. Interactions within a layer dominate, with those between adjacent layers much smaller and those between remoter layers negligible. Tilt affects the interactions more than the detailed lattice structure does. The results provide a key ingredient for theories of the optical and electrical properties of Langmuir–Blodgett films.