Modelling of lattice defects in advanced materials

These days, the effective development of new materials is a priority of research and industry in modern society. However, the basic description of material structure is insufficient to achieve detailed understanding of behaviour of many advanced materials. Here the studies of structure defects become more and more important. At this level of research, the theoretical modelling, such as ab initio calculations, serves as very effective approach as it provides information which is experimentally inaccessible. In our group, we use the VASP code with projector-augmented plane wave (PAW) potentials which, in combination with the IT4I computational resources, forms very effective tool for material research. In our presentation, we will present several case studies of lattice defects including the disorder in sublattices in Fe-Al-Co system and grain boundaries in fcc Ni containing vacancies and segregated impurities. We will show typical problems and challenges we face (optimization of cell size and shape, appropriate choice of defect position or correct choice of structure relaxation method) and solutions we use. Also, some typical material characteristics that can be obtained by our calculations will be presented, such as heats of formation, equilibrium structure configurations, segregation energies of impurities at grain boundaries or energies of vacancy formation.