ELFT HÍRADÓ

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SZFI SzemináriumPodmaniczky FrigyesMTA Wigner FK SZFIPhase-field crystal 
modeling of nucleation and growth processes - PhD házi védés2023. június 29. 
csütörtök, 10.00, KFKI Telephely, I. épület 1. emeleti TanácsteremThe first 
rigorous treatment of the solid-liquid transition dates back to the work of 
Ramakrishnan and Yussouff from the late 70’s, which connected the homogeneous 
liquid with the highly inhomogeneous phase within a single microscopic order 
parameter theory. This served as inspiration for the modern classical density 
functional theories of solidification. However, these models suffer from poor 
numerical efficiency due to the resolution required for the accurate 
representation of the structural correlations of the homogeneous liquid. In 
the early 2000’s Elder et al. have managed to formulate a one-mode 
approximation to the same physical phenomenon, termed the phase-field crystal 
(PFC) model [1], which is numerically less demanding, yet qualitatively 
accurate and managed to track the temporal evolution of systems on the 
micrometer scale. A significant advantage of the PFC model over 
coarse-grained phase-field models is, that the choice of the order parameter, 
namely the one-particle average density is inhomogeneous in the equilibrium 
solid phase and carries the same symmetries as the crystal. This leads to the 
natural coupling of elastic effects to thermodynamics, without the use of ad 
hoc auxiliary fields. Within the PFC framework, I have analysed [2] the 
structural signatures of solid clusters, that develop in quenched liquids, 
prior to the appearance of BCC crystals. The mechanism behind the formation 
of polycrystalline clusters, initiated from a single perfect crystal will be 
elucidated, which gives a microscopic explanation of such complex growth 
forms as spherulites. I have also made progress in the understanding of 
defect formation during strained epitaxial growth, the importance of the 
kinetic pathways to defect formation as opposed to equilibrium energy balance 
arguments will be considered. [1] K. R. Elder, M. Katakowski, M. Haataja, M. 
Grant, Phys. Rev. Lett. 88, 245701 (2002) [2] L. Gránásy, Gy. I. Tóth, J. 
A. Warren, F. Podmaniczky, Gy. Tegze, L. Rátkai, T. Pusztai, Prog. Mat. Sci. 
106, 100569 (2019) Minden érdeklődőt szívesen látunk! - Everyone is 
welcome to attend.Nagy Attilasem-admin AT szfki.hu