Excess entropy of mixing for binary square-well fluid in the mean spherical approximation: Application to liquid alkali-metal alloys

• Mean spherical approximation is used to treat the square-well model.
• Semi-analytical procedure is used to treat the mean spherical approximation.
• Expression for the entropy of binary square-well mixture is derived.
• This expression is applied to liquid Na-K and Na-Cs alloys.
• The concentration dependencies of the excess entropy of mixing are calculated.

The expression for the entropy of binary square-well (SW) mixture is derived in the framework of the semi-analytical approach [J. Non-Cryst. Solids 353 (2007) 1798] for the mean spherical approximation. This expression is applied to calculate the concentration dependencies of the excess entropy of mixing for liquid Na-K and Na-Cs alloys at T = 373 K. It is shown that the SW model allows to achieve a better agreement with experiment than the hard-sphere model with the same values of hard-core parameters.