 Hamaker estimate of liquid surface tension

For two liquid half-spaces, integrate the magnitude of a dispersion attraction per area $A_H/(6\pi h^3)$ from a molecular contact cutoff $h_0$ to infinity. The work per area is $A_H/(12\pi h_0^2)$. Because cleavage creates two interfaces, each has the displayed surface tension in this approximation. The cutoff is essential: a continuum attraction cannot describe atomic overlap and short-range repulsion. This estimate neglects interfacial entropy, detailed density profiles and nonadditive interactions, and it cannot replace the metallic bonding or hydrogen bonds that dominate some liquids' cohesion.