and Simulation 1

Contributed talk

Ab initio predicted phase stabilities of complex materials at finite temperatures

Tilmann Hickel, Max-Planck-Institut für Eisenforschung, Düsseldorf, Germany
Biswanath Dutta, Max-Planck-Institut für Eisenforschung, Düsseldorf, Germany
Blazej Grabowski, Max-Planck-Institut für Eisenforschung, Düsseldorf, Germany
Fritz Körmann, Max-Planck-Institut für Eisenforschung, Düsseldorf, Germany
Mehmet Acet, Universität Duisburg-Essen, Duisburg, Germany
Jörg Neugebauer, Max-Planck-Institut für Eisenforschung, Düsseldorf, Germany

Ab initio methods based on density functional theory are meanwhile an important part of multiscale materials simulation. Their atomistic view on physical processes and the access to chemical trends are attractive for a knowledge-driven development of novel electronic, biological or engineering materials. However, the apparent restriction of the method to ground state properties is a severe challenge for the understanding and prediction of many materials properties, as, e.g., heat capacities and phase diagrams, for which finite temperature effects are decisive. Over the last years we have developed a large range of multi-physics tools to go beyond these limitation. A key challenge was and is the accurate determination of free energies including all relevant excitation mechanisms individually as well as non-adiabatic coupling effects stabilizing certain phases.

With the present contribution, we will discuss some of our recent methodological developments that foster a large-scale screening of material properties, even at temperatures where anharmonic lattice vibrations and magnetic disorder become important. The finite-temperature ab initio methods will be applied to the calculation of martensitic and intermartensitic phase transitions in Ni-Mn-X Heusler alloys. The predicted chemical trends are important for a tailored design of their magnetocaloric and shape-memory properties, which sensitively depend on the microstructure of the martensite. The methodological developments and the applications to the material system have been performed with several partners within the Materials Chain.

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