ICAMS / Interdisciplinary Centre for Advanced Materials Simulation


The solubility of carbon in bcc iron under volumetric strain: comparison of DFT and empirical methods

Date: 24.10.2010
Place: 468. Wilhelm und Else Heraeus-Seminar "Ab initio Description of Iron and Steel: Mechanical properties", Ringberg Castle, Tegernsee, Germany

Elisaveta Hristova, Universität des Saarlandes, Saarbrücken, Germany
Rebecca Janisch
Ralf Drautz
Alexander Hartmaier

With the aim of investigating the interaction of C with dislocations in Fe by large scale molecular dynamics, we evaluate the transferability of different semiempirical potentials. As a test case the carbon solubility in bcc Fe as a function of lattice strain is studied by ab-initio calculations based on density-functional theory (DFT) and by four different empirical potentials of the embedded-atom method as (EAM) well as the modified EAM (MEAM). Both DFT and (all but one) empirical potential calculations predict that the carbon solubility increases with increasing volumetric strain, up to the maximum applied strain of five percent. However, the enthalpy of formation for this interstitital defect remains positive throughout the whole range of strains. Interestingly, the enthalpy of formation obtained by DFT is much more strain-sensitive than the one obtained by the empirical potentials. The different description of the carbon solubility in the presence of strain fields by the four empirical potentials is due to different parametrization, construction and fitting of the EAM potentials, and in the case of the MEAM to the different formalism including angular dependent bonding.

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