Equation Of State And Phase Transition To First Order For Argon-Like Fluids

Argon-like fluid is such a fluid system as constructed by atoms or molecules as simple as Argon atom. Along with the development of experimental techniques and the universal application of concurrent computers, the database of physical behavior of Argon-like fluid in its liquid-phase transition to first order is very accurate now. The database is described always by some empirical equations of state. There is no suitable theoretical interpretation about the database till now. To view with microcosmic opinion, phase transition origins from the interaction among atoms or molecules. To view with statistical physics, different interaction is corresponsive with different Hamilton function. Following, different physical behaviors appear. Thus it is an important work to found a statistical model to offer a suitable interpretation to the database above.In the present thesis, using pair-wise interaction function, a statistical model for Argon-like fluid is founded. Lots of theoretical results obtained from this model are compared with the database above. On theoretical opinion, this model works well. Firstly, a potential function with temperature factor T~s is developed to describe the pair-wise interaction instead of Debye, Keesom and London's results. By applying this potential function to Eyring's statistical theory, it is found that this potential function plays a role in describing the physical behaviors of Argon-like fluid, especially, the phenomenon of liquid-gas phase transition to first order. Then attention is paid to the hard-core equation of state which empirically well describes the physical behaviors of fluids. A new attractive term is mentioned out and instead of the famous van der Waals attractive term. Calculations denote that this new attractive term contains the van der Waals attractive term and deduces the experimental critical compressibility factor of Argon and other matters briefly. In order to find the relation between this attractive term and the pair-wise interaction, the model called average distribution is founded. By applying Sutherland potential to this model, the new attractive term above is derived. By applying Lennard-Jones potential to this model, it is found that Lennard-Jones potential, which is widely used as the pair-wise interaction in DFT theory and IEM, maybe not a good potential function. Then polynomial potential function is applied to this model. The famous Virial equation of state is obtained. The principle of correspondingstate of latent heat is offered under the model. When this model is combined with the theory of excluded volume, experimental critical compressibility factor and Boyle value are obtained together.