Project title: Mesoscopic size eff ects on organic ferroelectrics

Supervisors: Dr Laura Ratcli ff and Prof Aron Walsh

Project description:
The recently discovered family of organic ferroelectric materials could become a cheaper, more environmentally friendly alternative to inorganic ferroelectrics such as barium titanate and potassium zirconate titanate for applications in optics, actuation, memory chips, and temperature sensing devices [1]. The majority of theoretical studies that have been carried out so far on organic ferroelectrics have focused on bulk properties e.g. [2, 3]; however, to accurately predict their potential, it is necessary to understand the impact of domains, grains and other defects on their ferroelectric, piezoelectric, and optical properties, similarly to how inorganic ferroelectrics have been investigated e.g. in [4].

The aim of this project is to develop theoretical and computational tools to efficiently simulate these mesoscopic size e ffects so that they can be fully understood and manipulated. We will carry out ab initio electronic structure and molecular dynamics calculations to understand the microscopic mechanisms that underpin the polarization switching and phase transitions of a range of organic ferroelectrics such as croconic acid [5]. These will then be used to parametrize computationally efficient models so that the mesoscopic size e ffects of interest can be captured.

[1] Sachio Horiuchi and Yoshinori Tokura. Organic ferroelectrics. Nature Materials, 7:357 EP - , May 2008. Review Article.
[2] Yaxuan Cai, Shijun Luo, Zhanwu Zhu, and Haoshuang Gu. Ferroelectric mechanism of croconic acid: A first-principles and monte carlo study. The Journal of Chemical Physics, 139(4):044702, 2013.
[3] Da-Wei Fu, Hong-Ling Cai, Yuanming Liu, Qiong Ye, Wen Zhang, Yi Zhang, Xue-Yuan Chen, Gianluca Giovannetti, Massimo Capone, Jiangyu Li, and Ren-Gen Xiong. Diisopropylammonium bromide is a high-temperature molecular ferroelectric crystal. Science, 339(6118):425{428, 2013.