ICAMS / Interdisciplinary Centre for Advanced Materials Simulation

Atomistic simulation of the kinetics of phase transformations

Jutta Rogal

The research group focuses on the development and application of methods for long time-scale atomistic simulations. The two main research areas are the diffusion of impurities in the presence point and extended defects (e.g. diffusion of d-band elements in Ni-based superalloys), and the kinetics of phase transformations (e.g. formation of topologically close-packed phases, martensitic transformation in high-temperature shape memory alloys, nucleation during solidification).

Change in energy along an adaptive kinetic Monte Carlo trajectory showing the transition from an A15 to a bcc structure in molybdenum.  The total simulation time reaches up to microseconds at a temperature of T=300 K.

Change in energy along an adaptive kinetic Monte Carlo trajectory showing the transition from an A15 to a bcc structure in molybdenum. The total simulation time reaches up to microseconds at a temperature of T=300 K.

Atomistic processes dominating the long-time dynamics of impurity diffusion, solid-solid phase transformations or nucleation belong to the class of so-called rare events. In this context, rare events comprise processes that require transitions between local minima of the potential energy surface that are separated by sizeable energy barriers. This leads to a separation of time scales between the short-time dynamics within each local minimum (e.g. lattice vibrations) and the long-time dynamics between the minima (e.g. diffusion, structural rearrangements), which makes it impossible to study such problems with classic molecular dynamics simulations. If the dynamics of the rare events can be described correctly based on the underlying atomistic processes, it is possible to follow the time evolution of a system over an extended time scale.

Within the group, various techniques such as accelerated molecular dynamics, kinetic Monte Carlo, or transition path sampling are utilised to investigate rare events.

Growing nucleus during solidification in nickel. The snapshot has been taken from a transition path sampling simulation.  The different colours denote different local structures: red for fcc, green for hcp, blue for bcc, rose for pre-structured and grey-transparent for liquid.

Growing nucleus during solidification in nickel. The snapshot has been taken from a transition path sampling simulation. The different colours denote different local structures: red for fcc, green for hcp, blue for bcc, rose for pre-structured and grey-transparent for liquid.

Group Members

 

Former Members

  • Dr. Yaojun Du
  • Dr. Ari Harjunmaa
  • Marco Rozgic
  • Dr. Sergej Shuwalow

Competences

  • nucleation and phase transformation
  • diffusion
  • (adaptive) kinetic Monte Carlo
  • transition path sampling
  • (accelerated) molecular dynamics

Recent publications

A. Ferrari, A. Paulsen, J. Frenzel, J. Rogal et al. Unusual composition dependence of transformation temperatures in Ti-Ta-X shape memory alloys Physical Review Materials, 2, 073609, (2018)

T. Chakraborty. Atomistic modelling of phase transitions in Ti-Ta high-temperature shape memory alloys PhD Thesis, Ruhr-Universität Bochum (2017)

H. Alvaro Galue, G. Díaz Leines. Origin of spectral band patterns in the cosmic unidentified infrared emission Physical Review Letters, 119, 171102, (2017)

Y. Liang. Nucleation in Ni-Al alloys - an atomistic study Master Thesis, Ruhr-Universität Bochum (2017)

T. Schablitzki, J. Rogal, R. Drautz. A kinetic Monte Carlo approach to diffusion-controlled thermal desorption spectroscopy Philosophical Transactions of The Royal Society A, 375, 20160404, (2017)

Contact

Dr. Jutta Rogal
ICAMS
Ruhr-Universität Bochum
44780 Bochum
Germany
Tel: +49 234 32 29317
Fax: +49 234 32 14977

Email: jutta.rogal@rub.de

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