Phase transitions at electrochemical interfaces: Evaluation of critical exponents for condensation of organic adsorbates

The surface pressure exerted by a monolayer of organic compounds condensing at electrochemical interfaces is evaluated using a two-dimensional nearest-neighbor Ising model formalism. The experimental critical temperature data of organic adsorbates are employed to obtain the composite short-range interaction energy using Onsager's exact solution. The methodology of obtaining the critical exponents 'δ' and 'γ' pertaining to surface pressure and isothermal compressibility is discussed. These values are consistent with the exponents postulated in other contexts, thereby demonstrating the universality hypothesis.