In the past century, scientists have successfully synthesized many new materials and studied their properties, but the purely experimental approach is no longer the only route to discover new compounds. There are several alternatives, which nowadays, one could say sometimes even give priority to the theory compared to the experiment, especially in the field of material science; First, the theoretical prediction of new compounds and new (meta)stable modifications of already existing molecules and solids, followed by their experimental synthesis, and second, the purely theoretical prediction of new compounds and new (meta)stable modifications of unknown compounds where there is no comparison to an experimental result is possible or where an experiment is not feasible at all. One might even say that we have come to the point where it is increasingly necessary for the presentation and discussion of experiments obtained in the field of the material sciences research, to verify or combine the experiment with theoretical calculations.
The crystal structure prediction , i.e. the search for new crystalline compounds followed by their synthesis has been an important topic of solid state chemistry in the past two decades. Crystal structure prediction we can define as the procedure which starts with no empirically based information on the positions of the atoms in the unit cell. The goal of structure prediction is the determination of as many of the low-lying local minima as possible. Both identifying the energetically favored candidate for a given set of thermodynamic parameters and finding the candidates that represent metastable modifications requires the use of a global optimization method, where in general we permit free variation of atom positions, cell parameters, ionic charges and composition. Beside the pure methods of structure modeling and structure prediction, many different classes exist which combine them without a strict boundary, e.g. determining the structures of already synthesized compounds, where only powder diffraction data are available but no successful structural model has been found or in crystal structure refinement, where an approximate structure is known and the energy is then minimized, in order to generate a more accurate model. There are many global optimization methods available, e.g. simulated annealing , genetic algorithm , basin hopping ,thermal cycling , and alternatively, the structure of a compound could be guessed from information obtained from past experiments.
Within this project, we perform structure predictions of new advanced materials, structural ceramics, geo-materials, bio-materials, nuclear materials and eco-materials, with the focus on the structure predictions of novel materials as well as (meta)stable modifications of the existing materials. These theoretical investigations are closely connected with the experimental work within the departments of the Center for Synthesis, Processing and Characterization of Materials for Application at Extreme Conditions (CEXTREME LAB) and Materials Science Laboratory (MSL).
- D. Zagorac, J. C. Schön, J. Zagorac, M. Jansen, Prediction of structure candidates for zinc oxide as a function of pressure and investigation of their electronic properties, Physical Review B – Condensed Matter and Materials Physics 89 (7) (2014), article number 075201. DOI: https://doi.org/10.1103/PhysRevB.89.075201
- J. Zagorac, D. Zagorac, M. Rosić, J. C. Schön, B. Matović, Structure prediction of aluminum nitride combining data mining and quantum mechanics, CrystEngComm 19(35) (2017) 5259-5268. DOI: https://doi.org/10.1039/c7ce01039g
- J. Luković, D. Zagorac, J. C. Schön, J. Zagorac, D. Jordanov, T. Volkov-Husović, B. Matović, Tungsten Disilicide (WSi2): Synthesis, Characterization, and Prediction of New Crystal Structures, Zeitschrift fur Anorganische und Allgemaine Chemie 643(23) (2017) 2088-2094. DOI: https://doi.org/10.1002/zaac.201700329
- D. Zagorac, J. Zagorac, J. C. Schön, N. Stojanović, B. Matović, ZnO/ZnS (hetero)structures: ab initio investigations of polytypic behavior of mixed ZnO and ZnS compounds, Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials 74(6) (2018) 628-642. DOI: https://doi.org/10.1107/S2052520618014099