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Metody obliczania napięcia międzyfazowego z symulacji komputerowych

Chrzanowski J., Lamperski S.

Wiadomości Chemiczne

2014

[Z] 68, 3-4

257--278

Interfaces have been recently a subject of profound interest for physicists, chemists and biologists because of the processes taking place in the interfacial region like adsorption, catalysis of chemical reactions etc. Computer simulations treat an interface in a full atomic level and by that they are a valuable complementary technique for experiment and theory. In this paper, different methods for the calculation of an interfacial tension by computer simulations are described and compared. The most commonly used method for the interfacial tension calculation was developed by Kirkwood-Buff. It is based on the mechanical route definition. This approach uses normal and tangential pressure components of the pressure tensor. The interfacial tension can be also evaluated through its thermodynamic definition. The method of Bennett defines the interfacial tension as the free energy difference of two (or more) systems relative to the difference in interfacial areas. The “test- -area” method is based upon the perturbation formalism. The test state is obtained from an infinitesimal change of the surface area of the reference system. The third method based on the thermodynamic route used to evaluate the interfacial tension is thought as an expanded ensemble simulation where two systems with different free energy and the interfacial area are connected by a discrete chain of intermediate subsystems. The next approach is based on the capillary wave theory formalism which provides a relationship between the surface tension and the wave width due the capillarity broadening. Interfacial tension may be also computed from the square gradient theory which is based on the expansion of the Hemholtz free energy in the Taylor series around the homogeneous state with the assumption that the molecular gradients in the interface are small compared to intermolecular distance. The theoretical basis, application and results of computer simulations of each method are presented. Aa accuracy of the methods in different simulation methodologies and systems is compared.