Dresden 2006 – wissenschaftliches Programm

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MM: Metall- und Materialphysik

MM 31: Symposium Materials Modelling I

MM 31.4: Fachvortrag

Donnerstag, 30. März 2006, 11:45–12:15, IFW A

Atomic-scale modelling of austenitic stainless steel — •Hans L. Skriver — CAMP, Technical University of Denmark

We have determined the stability of a ternary alloy of Fe, Cr, and Ni in the austenitic γ-FeNi phase including interstitial nitrogen and carbon by a variety of computational methods and approximations: the full charge density Exact Muffin-tin Orbitals (EMTO) method for accurate determination of formation energies, the order-N Locally Self-consistent Green Function (LSGF) method for efficient treatment of large supercells with a single interstitial nitrogen atom, and the Linear Muffin-Tin Orbitals (LMTO) method in conjunction with the Coherent Potential Approximation (CPA) and the Generalized Perturbation Method (GPM) for the calculation of the effective cluster interactions used in Monte Carlo simulations.

We find that the stability of nitrogen and carbon in the octahedral sites depends mainly on the number of Cr atoms in the first coordination shell. The calculated relative solution energies of nitrogen in γ-FeNi as a function of the local octahedral configuration and the abundance of the different octahedral configurations obtained in the Monte Carlo simulations as a function of temperature form the basis for a discussion of the experimental uptake curves for nitrogen in stainless steel.