SPP 1296:  Heterogeneous Nucleation and Microstructure Formation: Steps towards a System- and Scale-bridging Understanding

• Subject Area: Materials Science and Engineering
• Term: from 2007 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 28442692

The goal of this Priority Programme is to attain a fundamental understanding of the basic mechanisms underlying heterogeneous nucleation as well as the subsequent development of the nucleus into a specific heterogeneous microstructure. In particular, a system and method-spanning scientific approach is intended to contribute to a detailed, multiscale understanding of these mechanisms, which is intended to be applied successively and system-independently on different kinds of material systems. Initially, this is planned for the simplest types of model systems for heterogeneous crystalline orders, for pure metals, binary metal alloys and colloids. Their liquid phase, which is the basis for crystalline nucleation, shall be specified via examinations of its physical properties and ordering characteristics. More specifically, the following questions are intended to be explored within the context of the Priority Programme:
(1) Heterogeneous nucleation: What does a critical nucleation grain look like? Does the classical concept of a contact angle make sense for heterogeneous nucleation? Can claims made about the dominant contributions to the nucleation barrier for heterogeneous nucleation, like they can be obtained from molecular simulations, be reconciled with data gained via the phase-field method? What is the relation between interaction potentials and the relevant boundary energies?
(2) Transition from nucleus to microstructure: How does microstructure develop out of a nucleus in the interplay between crystallisation and segregation depending on the precise reference point in the phase diagram? How stable are those scenarios with respect to changes of that reference point? How well can these scenarios are reproduced via binary colloidal model systems?
(3) Microstructure development: What kind of consequences result from the new understanding of nucleation for the initial development of the microstructure? What kind of kinetic rules does the initial growth of the solidifying microstructure follow? Is it possible to identify universal conditions, under which several microscopic morphologies of the same alloy composition are kinetically stable?
As well as the preparation the chemistry of the colloidal model systems are not in the focus of the programme.

• DFG Programme: Priority Programmes
• International Connection: Luxembourg, Switzerland

Projects

• A continuum model for heterogeneous nucleation - atomistic simulations on diffusive time scales (Applicant Voigt, Axel )
• Advanced MD simulations of heterogeneous nucleation of binary colloids (Applicant Holm, Christian )
• Anisotropy of the solid liquid interface and its effect on heterogeneous nucleation in aluminium-based melts (Applicant Brillo, Jürgen )
• Computer simulation of heterogeneous nucleation and crystal growth in metallic alloys (Applicant Horbach, Jürgen )
• Computer simulation of heterogeneous nucleation of colloidal crystals at planar walls (Applicant Virnau, Peter )
• Coordination of SPP 1296 (Applicant Emmerich, Heike )
• Coupled phase-field and phase-field crystal studies to bridge the atomic to micro-scale in heterogenous nucleation (Applicant Emmerich, Heike )
• Density functional theory of heterogeneous nucleation and microstructure formation (Applicant Löwen, Hartmut )
• Elastic effects on heterogeneous nucleation and microstructure formation (Applicants Müller-Krumbhaar, Heiner ;  Spatschek, Robert )
• Grain Refinement and Microstructure Formation by Inoculation (Applicants Apel, Markus ;  Günther, Robert ;  Pyczak, Florian )
• Heterogeneous Nucleation and Crystal Growth in Colloidal Model Systems Studied by Confocal Microscopy (Applicant Maret, Georg )
• Heterogeneous nucleation and microstructure formation in binary colloidal systems (Applicant Bechinger, Clemens )
• Heterogeneous nucleation and microstructure formation in colloidal crystals (Applicant Schöpe, Hans Joachim )
• Heterogeneous nucleation and microstructure formation in peritectic alloy systems (Applicants Emmerich, Heike ;  Schmid-Fetzer, Rainer )
• Heterogeneous nucleation of metals and colloids on templates - a comparative study (Applicant Herlach, Dieter M. )
• Kinetics of heterogenous nucleation and growth (Applicant Wilde, Gerhard )
• Microstructure formation in charged sphere colloidal crystals after heterogeneous nucleation (Applicant Palberg, Thomas )
• Scale-bridging phase-field simulations of microstructure responses on nucleation in metals and colloids (Applicant Nestler, Britta )
• Simple model systems: Static and dynamic aspects of heterogeneous nucleation within simulation, phase field crystal and dynamic density functional theory (Applicant Oettel, Martin )
• The role of seeds in heterogeneous nucleation, growth and ripening: A quantitative confocal microscopy and scattering study (Applicants Egelhaaf, Stefan U. ;  Richtering, Walter )

• Spokesperson: Professorin Dr.-Ing. Heike Emmerich