Test Case 9: A surfactant at the air-water interface

The system is comprised of 32 surfactant molecules (trimethylaminododecane bromide or TAB-C12) arranged either side of a slab of 342 water molecules approximately 30 $\AA$ thick. The surfactant chains are treated with rigid bonds and the water molecules are treated as rigid bodies. The TAB headgroup has fractional charges summing to +1 (the bromide ion has charge -1). The Ewald sum handles the electrostatic calculations. The short range forces are taken from the Dreiding force field.