Séminaire Théorie

Mardi 10 Mai 2016 à 11h00.

Application of Hill’s thermodynamics of small system to molecular systems

''Before reaching the thermodynamic limit, different intensive thermodynamic properties change with the system size. This is particularly the case for partial molar quantities like the partial molar enthalpy or internal energy. This effect is mainly due to the fact that the system has a finite volume so it exhibits a surface, virtual or not, that affects the values of the properties. For partial molar quantities, it can also be seen like an effect of the volume of the particles on a limited volume. The thermodynamics of small system of T. L. Hill [1] gives a general background to systematically express these thermodynamic properties in terms of system size [2]. Alternatively to Hill’s approach similar size effects were obtained using the Kirkwood-Buff’s formalism based on pair correlation functions [3]. We applied these size properties on molecular simulations to calculate at the thermodynamic limit the thermodynamic factor, i.e. the derivative of the chemical potential with the concentration, in open systems [2, 3, 4, 5, 6]. Following the same approach, we also computed partial molar enthalpy and partial internal energy [7]. This was done on systems were other methods fail to compute such thermodynamics properties. [1] T. L. Hill. Thermodynamics of small systems. Part 1, Benjamin, New York, 1963. [2] Thermodynamics of small systems embedded in a reservoir: a detailed analysis of finite size effects S. K. Schnell, T. J. H. Vlugt, J.-M. Simon, D. Bedeaux, S. Kjelstrup, Mol. Phys. 110, 1069 (2012) [3] Kirkwood-Buff Integrals for Finite Volumes, P. Kruger, S. K. Schnell, D. Bedeaux, S. Kjelstrup, T. J. H. Vlugt, J.-M. Simon, J. Phys. Chem. Lett., 4, 235 (2013) [4] How to apply Kirkwood-buff theory of individual species in salt solutions, S. K. Schnell, P. Englebienne, J.-M. Simon, P. Kruger, S. P. Balayi, S. Kjelstrup, D. Bedeaux, A. Bardow, T. J. H. Vlugt, Chemical Physics Letters 582, 154 (2013). [5] Diffusion Coefficients from molecular dynamics in binary and ternary mixtures, X. Liu, S. K. Schnell, J. M. Simon, P. Kruger, D. Bedeaux, S. Kjelstrup, A. Bardow, T. J. H. Vlugt, Int. J. of Thermophys, 34, 1169 (2013). [6] Calculation of chemical potential and activity coefficient on two layers of CO2 adsorbed on a graphite surface, T.Trinh, D. Bedeaux, J.-M. Simon, S. Kjelstrup, PCCP, 17, 1226 (2015). [7] Partial molar enthalpies and reaction enthalpies from equilibrium molecular dynamicsSimulation, S. K. Schnell, R. Skorpa, D. Bedeaux, S. Kjelstrup, T. J. H. Vlugt, J.-M. Simon, J. Chem. Phys. 141, 144501 (2014)''