by on

Mike Evans and I have just published our second article together, in the Royal Society of Chemistry’s interdisciplinary journal Soft Matter. It concerns a simulation study of crystal growth in the presence of two common complicating factors: i) Polydispersity (particles are non-identical) and ii) Metastability (in addition to the crystal growth, non-equilibrium gas-liquid separation is taking place). The result is the “boiled-egg” growth mechanism, which we model with theory and simulation, and whose effects on growth depend on a subtle interplay between the two factors I just mentioned, which remains to be further explored. The work is of generic relevance to many situations, but particular examples include e.g. protein crystallisation, photonic crystal growth, colloid-polymer mixtures. There are looooooads of nice pictures in this one.

  • The advance online article is here.
  • A pre-print which I will shortly update with the final small changes we made before publication (freely accessible to everyone but with less pretty formatting and editing etc.) is here.

Enjoy!

 

by on

I’ve just uploaded a preprint of a new paper me and my supervisor are writing to arXiv. It’s a freely-available repository research in loads of different areas which people use to make research available before and while its in peer review for a journal.

This one is to do with crystal growth in soft condensed matter. That includes colloidal crystals and closely related things such as proteins, which must be crystallised in order to study their structure in biological/medical research. The broad question of ‘What’s the best way to grow a crystal?’ is relevant in a lot of scenarios, especially given that one is often quite free to vary the conditions in the system to optimise growth; for instance the interactions in a e.g. colloidal suspension can be easily tuned by adding other species such as polymer coils into the solution.

The dynamics of phase transitions, i.e. how systems do or do not actually reach their true equilibrium state, is an important consideration in applying thermodynamics to soft matter. In this paper, we simulate crystal growth (as shown in the video here) in the presence of metastable gas-liquid separation, which may be encouraged or avoided by tuning the interaction potential in a system, and polydispersity, which usually cannot be avoided in soft matter. There’s a variety of nice visualisations showing the effects of these two factors on the crystal growth dynamics, and we find that they can interact in a complex and previously unknown way. The simulation findings are related to existing experimental data and to theoretical considerations. Here’s the link:

The effect of metastability and polydispersity on crystal growth kinetics

This work, in early form, was the subject of a recent internal seminar in the Soft Matter Group at Leeds. I’ve uploaded the slides and an audio recording from the seminar.