Monte Carlo simulation of carbon activity in BCC iron

The research problem is to verify the literature-proposed values of carbon atomic interactions in BCC iron for various coordination spheres. The goal hereof is to compute the carbon activity in BCC iron using various carbon-atom interaction parameters. Methods: An author-coded Monte Carlo program is used for simulation; the program analyzes a supercell comprised of 20×20×20 unit cells of body-centered cubic (BCC) iron. The paper presents a successfully optimized solution that attains convergence of averaging at 500 Monte Carlo steps. Computations are performed for a wide temperature range (T = 955, 975, 1000, 1026, 1056, 1070, 1086, 1121 K). Results: Computations show that virtually all of the proposed parameterizations are consistent with the experimental data, as carbon-atom barely interact at low concentrations. Computations are further expanded to cover higher-than-real concentrations to study how carbon atoms could affect the activity curve. This enables a comparison of various parameterizations, bringing a few interesting findings. Besides, the research demonstrates that experimental carbon activity curves can be reproduced for multiple C-C interaction configurations. The novelty of this research is that computing the energy of C-C interaction for the first four coordination spheres suffices for computing the carbon activity in BCC iron. The practical significance is that the research has produced new theoretical data that will be made use of when developing new steel grades and designing new thermal-treatment processes.