Improved energy minimization of iron-carbon systems: on the influence of positioning interstitial atoms

N Gunkelmann and M Merkert, MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING, 28, 045005 (2020).

DOI: 10.1088/1361-651X/ab6bb6

We compare different optimization schemes for the energy minimization in iron-carbon single crystals, where either choosing an initial distribution of interstitial atoms is followed by a conjugate gradient algorithm, or a simulated annealing (SA) procedure is employed. As an alternative to random or so-called single-atom starting configurations, globally optimal interstitial sites with respect to a long-range potential for the carbon-carbon interaction are computed by exact methods of discrete optimization. A comparison of the mechanical properties of the corresponding systems reveals that the positioning scheme can have a large influence. The elastic properties of the crystals for initially randomly distributed carbon atoms show large fluctuations for different initial C interstitial positions. The solution by SA is superior but still causes significant deviations, while using the optimized configurations leads to an increased stiffness of the Fe-C system.

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