tailieunhanh - Thermodynamics Interaction Studies Solids, Liquids and Gases Part 7

Tham khảo tài liệu 'thermodynamics interaction studies solids, liquids and gases part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 350 Thermodynamics - Interaction Studies - Solids Liquids and Gases Here Sịị is the energy of interaction and ơịị is the minimal molecular approach distance. In the integration over v mt the lower limit is r ơịị . There is no satisfactory simple method for calculating the pair correlation function in liquids although it should approach unity at infinity. We will approximate it as r Ằ 1 ố 7 7 25 With this approximation we assume that the local distribution of solvent molecules is not disturbed by the particle under consideration. The approximation is used widely in the theory of liquids and its effectiveness has been shown. For example in Bringuier Bourdon 2003 2007 it was used in a kinetic approach to define the thermodiffusion of colloidal particles. In Schimpf Semenov 2004 Semenov Schimpf 2000 2005 the approximation was used in a hydrodynamic theory to define thermodiffusion in polymer solutions. The approximation of constant local density is also used in the theory of regular solutions Kirkwood 1939 . With this approximation we obtain N b AV Ao ằ j r dv 26 The terms under the summation sign are a simple modification of the expression obtained in Bringuier Bourdon 2003 2007 . In our calculations we will use the fact that there is certain symmetry between the chemical potentials contained in Eq. 11 . The term 4 can be written asNik Uk where Nik is w vk the number of the molecules of the k th component that can be placed within the volume Vị but are displaced by a molecule of i th component. Using the known result that free energy is the sum of the chemical potentials we can say that NikJuk is the free energy or chemical potential of a virtual molecular particle consisting of molecules of the k th component displaced by a molecule of the i th component. For this reason we can extend the results obtained in the calculations of molecular chemical potential fiiv of the second component to calculations of parameter NikJukv by a simple change in the respective .