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چکیده
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In the previous work a new simple approach was introduced to derive the LJ parameters for rare gases and n-allkans at any desired temperature between triple point to boiling point. The method was based on the experimental heat of vaporiziation data, free energy of solution, application of Sealed- Particle- Theory (SPT) and othjer new expressions that give the free energy of cavity formation, Gc, in hard sphere fluids. we have found that the LJ parameters are temperature dependent and decrease with increasing the temperature. Application of Chandler, weeks, Anderson. Verlet and weis (CWAVW) theory to 53 organic liquids at different temperatures (triple - boiling points) also indicates that Lennard-Jones pair potential parameters arc not constant and are dependent on temperature, so as temperature increases σ increases and ε/k decreases. Therefore this can be concluded that while the LJ (6-12) pail-potential is being used in any kind of theoretical work the variation of σ increases and ε/k values with temperature and hence temperature dependent of LJ potential function, U(r,T) =4 ε (T) [(σ(T)/r)12-(σ(T)/r) 6)] have to be taken into account.
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