Calculation of the Thermodynamic Characteristics of Fe–P System by the Molecular Dynamics Method

The problem of dephosphorization of iron-carbon alloys is relevant for the metallurgical industry, since a high concentration of phosphorus contributes to the appearance of a number of extremely undesirable phenomena. A lot of experimental work has been devoted to solving this problem, but it has still not been completely possible to cope with it. Any field experiments aimed at studying the process of phosphorus removal require considerable material and time costs, but at the same time do not guarantee getting the desired result. Therefore, to search for new approaches to solving this problem, it is much more rational to use numerical simulation methods involving the computational capabilities of modern computers. At present, computer experiments are the same recognized research method as theoretical research and real experiment. To study the behavior of phosphorus atoms in iron using a numerical experiment, it is necessary to build a computational model and test it by calculating various characteristics whose values are known in advance. In this paper, the method of molecular dynamics was chosen as the method of computer simulation. Using this method, one can conduct experiments with given atomic velocities and describe dynamics of the studied processes. To describe the interparticle interaction, we used the potential calculated in the framework of the immersed atom method. The study was conducted on a computational cell simulating α-iron crystal with phosphorus substitution atoms. The constructed model demonstrated satisfactory results when calculating the known characteristics of the simulated system. Dependencies of changes in such characteristics as temperature coefficient of linear expansion, melting point, latent heat of melting and heat capacity on the concentration of phosphorus atoms, as well as in some cases on magnitude of the applied external pressure, were established. Calculations showed that, for example, the phosphorus concentration of 0.5% leads to an increase in the average thermal coefficient of linear expansion by 9%, a decrease in temperature and latent heat of fusion by 5% and a heat capacity by 7%.