Relation between the Surface Tension and Roughness of the Intrinsic Liquid Surface

Previously published computer simulation data concerning the surface tension and surface roughness of various different liquid systems (i. e., binary water-methanol and water-dimethyl sulphoxide (DMSO) mixtures, water-poly-(ethylene-oxide) systems containing adsorbed sodium dodecyl sulphate, and room temperature ionic liquids) are re-analysed in order to find a relation between these quantities. It is found that the amplitude of the molecularly wavy liquid surface is inversely proportional to the logarithm of the surface tension while no clear correlation between the periodicity of the wavy surface and the surface tension is observed. It is also seen that the determination of the roughness parameters in a way analogous with the Langmuir formalism results in considerably more robust values than when an extra parameter is introduced in the procedure using a formula in analogy with the Langmuir-Freundlich isotherm.