PHASE-TRANSITIONS AT ELECTROCHEMICAL INTERFACES - EVALUATION OF CRITICAL EXPONENTS FOR CONDENSATION OF ORGANIC ADSORBATES

The surface pressure exerted by a monolayer of organic compounds conde nsing at electrochemical interfaces is evaluated using a two-dimension al nearest-neighbor Ising model formalism. The experimental critical t emperature data of organic adsorbates are employed to obtain the compo site short-range interaction energy using Onsager's exact solution. Th e methodology of obtaining the critical exponents 'delta' and 'gamma' pertaining to surface pressure and isothermal compressibility is discu ssed. These values are consistent with the exponents postulated in oth er contexts, thereby demonstrating the universality hypothesis. (C) 19 98 Elsevier Science B.V. All rights reserved.