Unified approach to scale transition in simulations of microstructure evolution using phase-field crystal modelBerčič, Matjaž (Avtor) Kugler, Goran (Mentor) phase-field crystalamplitude expansiongrain growthmicrostructure modellingThe Phase-Field Crystal model (PFC) is a model that is able to describe material on the atomic level across diffusive time scales using a continuous atomic density field. Its amplitude expansion (APFC) reformulates the model in a form suitable for the application of adaptive mesh refinement techniques. This thesis presents improvements to the APFC model that lead to effective use of adaptive mesh refinement techniques. An auxiliary field describing local grain rotation is introduced and used to enable the adaptive mesh to coarsen in all grains, regardless of their orientation. Only a Cartesian representation of the amplitude equations is employed. The introduced algorithm extracts the local grain rotation and exploits the rotational covariance of the amplitude equations to achieve efficient use of computational resources. The auxiliary local rotation field is used to remove an unphysical grain boundary present in the APFC model between grains, which are rotated by the crystal’s symmetry rotation. The unphysical grain boundary is removed by correctly matching the complex amplitudes describing the best aligned density waves. This corrects the grain boundary energies in half of the grain boundaries formed between the randomly rotated grains and enables APFC simulations of processes where grain rotation occurs. Simulations of a single rotating grain using the PFC and APFC models show qualitatively matching results, confirming the effective removal of the unphysical grain boundary under conditions where grains rotate dynamically. Together, the improvements enable microstructure simulations with the APFC model on an adaptive computational mesh, which efficiently distributes computational resources even in simulations of processes where grains rotate.20192019-06-01 07:45:03Doktorsko delo/naloga107871sl