The prestigious Materials Design Advanced Graduate Research Prize has been awarded to Joe Fallon

The prestigious Materials Design Advanced Graduate Research Prize has been awarded to Joe Fallon. 

This prize of £600 is kindly sponsored by Materials Design (www.materialsdesign.com) to acknowledge the CDT student who has demonstrated the most significant progress during their second year of PhD study. Recognising the strength of all candidates, Prof. Peter Haynes commented on the difficulty of allocating this award, but remarked that “the committee was particularly impressed by Joe's achievements in successfully spanning length- and time-scales in a very challenging system."

Joe’s research focuses on ferroelectric materials, which are used in a wide range of applications from fast random access memories to gate oxide transistors. The industrial drive towards ever  smaller ferroelectric devices has created a need to understand their properties on the atomistic scale, and Joe’s aim is to simulate ferroelectrics at the mesoscopic length scale while retaining the accuracy of full atomistic quantum-mechanical simulations. To this end he has created a classical force-field for the ferroelectric barium titanate (BTO) which accurately reproduces many properties (such as phonon modes) as calculated via density-functional theory (DFT).

Following on from DFT investigations of the potential energy surface of BTO, Joe has further used DFT to parameterise an atomistic force-field for BTO using force matching methods. According to Dr Arash Mostofi (one of Joe's supervisors) "the force-matching approach is rather challenging in this case", referring to the complexity of the true potential energy surface, and the subtle sensitivity of ferroelectricity to volume. Despite these challenges, Joe has succeeded in making a force field that reproduces the DFT structures and phonon bands to a very high level of accuracy. The phonons of his force-field give as good an agreement as those in the existing literature despite the fact that the vast majority existing force fields have been parameterised by fitting directly to the phonons---a process that Joe has avoided. 

“The multi-scale aspects of my project are the most challenging,” Joe remarked, echoing the thoughts expressed by both Peter Haynes and Arash Mostofi on the complexity of performing multi-scale work. “I spent a long time on DFT calculations and then had to jump suddenly to molecular dynamics simulations. The fact that I’ve been working within the CDT community has been extremely useful because when I need to learn a new technique I am able to chat to fellow students who have already been using it and learn from their advice and experience.”

Having an accurate atomistic force-field for BTO will enable Joe to study fundamental questions regarding this material, for example, the precise nature of the paraelectric–ferroelectric transition, surface and domain boundary structures, and how the Curie temperature varies with sample thickness. The CDT wishes him the best of luck with his future research.