نوع مقاله : مقاله پژوهشی
گروه فیزیک، دانشگاه پیام نور مرکز همدان
عنوان مقاله [English]
This study is devoted to the estimate the longitudinal, bulk and shear stress auto correlation functions (LSAC/BSAC/SSAC) and corresponding viscosities of evaporated Na for four thermodynamic states. In fact, this study is devoted to investigating temperature dependence of BSAC/LSAC/SSAC functions. This expression is written as a time integral of a time correlation function of a quantity corresponding to the transport coefficient. To investigate transport coefficients theoretically, the method used more frequently is the Green-Kubo formula. Another quantity required to evaluate the LSAC/BSAC/SSAC functions is the distribution function. For this aim, we have used the results work of Kahl and Kambayashi having been done via molecular-dynamics (MD) simulation method. First, three non-zero sum rules for the longitudinal and bulk stress auto correlation functions have been evaluated. For the interaction potential, we have used Ashcroft pseudo potential and corresponding pair correlation function. The Green-Kubo method and Mori memory function formalism coupled with the frequency sum rules have been used to calculate the viscosities. The estimate of the shear, bulk and longitudinal viscosities of evaporated Na for four thermodynamic states has been presented.