THE PHASE-TRANSITION IN AMPHIPHILIC MONOLAYERS - ISOTHERMS IN THE CLUSTER VARIATION METHOD

Citation
C. Buzano et Lr. Evangelista, THE PHASE-TRANSITION IN AMPHIPHILIC MONOLAYERS - ISOTHERMS IN THE CLUSTER VARIATION METHOD, Journal of physics. Condensed matter, 6(28), 1994, pp. 5323-5334
Citations number
28
Categorie Soggetti
Physics, Condensed Matter
ISSN journal
09538984
Volume
6
Issue
28
Year of publication
1994
Pages
5323 - 5334
Database
ISI
SICI code
0953-8984(1994)6:28<5323:TPIAM->2.0.ZU;2-6
Abstract
The liquid-expanded (LE)-liquid-condensed (LC) phase transition in mon olayers of amphiphilic molecules is investigated in the pair approxima tion of the cluster variation method. The model analysed is the model proposed by Firpo et al which can be mapped into the Blume-Emery-Griff iths Hamiltonian. The signatures of the LE-LC transition are searched for as break points on the isotherms of the surface pressure-molecular area diagram. The results obtained in the pair approximation are impr oved with respect to those obtained in the Bragg-Williams approximatio n for a set of typical energy and entropy parameters in the case of pe ntadecanoic acid. In particular, the LE-LC phase transition is shown t o be weakly first order. A comparison with experimental results gives satisfactory agreement.