Role of binding energy (edge-to-face contact of mineral platelets) in the acoustical properties of oceanic mud sediments

Abstract

A theory for mud sediments presumes a card-house model, where the platelets arrange themselves in a highly porous configuration; electrostatic forces prevent face-to-face contacts. The primary type of contact is where the edge of one platelet touches a face of another. Why such is not also prevented by electrostatic forces is because of van der Waals (vdW) forces between the molecular structures within the two platelets. A quantitative assessment is given of such forces, taking into account the atomic composition and crystalline structure of the platelets, proceeding from the London theory of interaction between non-polar molecules. Double-integration over both platelets leads to a quantitative and simple prediction for the potential energy of vdW interaction as a function of the separation distance, edge-from-face. At moderate nanoscale distances, the resulting force is attractive and is much larger than the electrostatic repulsion force. But, at very close (touching) distances, the intermolecular force becomes also repulsive, so that there is a minimum potential energy, which is identified as the binding energy. This finite binding energy, given a finite environmental temperature, leads to some statistical mechanical theoretical implications. Among the acoustical implications is a relaxation mechanism for the attenuation of acoustic waves propagating through mud.