Regensburg 2016 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 8: Topical session: Integrated computational materials engineering for design of new materials II

MM 8.5: Vortrag

Montag, 7. März 2016, 13:00–13:15, H38

Thermal properties of paramagnetic α-Mn from first principles — •Hossein Ehteshami and Pavel A. Korzhavyi — Materials Technology, Deptartment of Materials Science and Engineering, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden

Mn is a common alloying element in steel. Therefore, its physical properties and their variation with temperature are of interest for thermodynamic modeling. α-Mn is a complex cubic phase that is stable between 0 and 1000 K and undergoes antiferromagnetic ordering below the Neel point of about 100 K. For an element with such complex crystal and magnetic structures, one can expect that the magnetic, electronic and vibrational degrees of freedom are coupled. Here we describe the paramagnetic phase of α-Mn at finite temperatures by decoupling adiabatically the "fast" (electronic and magnetic) and "slow" (vibrational) degrees of freedom. The electronic structure is calculated within the exact muffin-tin orbital (EMTO) formalism. Electronic excitations are included via finite-temperature smearing of the Fermi function. Paramagnetic disorder is treated self-consistently in the disordered local moment (DLM) model and coherent potential approximation (CPA). The so obtained partial free energies (including the electronic and magnetic contributions as functions of temperature and volume) are used as the input to the Debye-Gruneisen model of the lattice vibrations. Thermal expansion, isothermal/adiabatic bulk modulus and specific heat capacities are calculated and compared with the experimental results to demonstrate the validity of the adiabatic treatment.