Conference on Computational Physics 2024

Junyi Zhu

Biographical Information:

Professor Zhu holds a PhD degree in Materials Science and Engineering from the University of Utah, and BS degree in Physics from Peking University, China. Since 2019 he has been an Associate Professor, Department of Physics, The Chinese University of Hong Kong, Hong Kong. In the period 2013-2019 he was an Assistant Professor in the same University. Research Interest are in Semiconductor defects and doping, Electronic properties of solids, Surface and interface phenomena, Using first principles and molecular dynamics approaches, Elastic theory modeling.


New Electron counting model based on layers and its application in the computational studies of phase change in transition metal oxides

Electron Counting model (ECM) has been proved to be a powerful tool in surface studies. However, most of the studies are focused on binary compound semiconductors and how to apply ECM to complex transition metal oxides is an open question. In this talk, I’ll introduce our recent discoveries on a new scheme of ECM that is based on an overall counting in a unit of one layer. Different from standard counting scheme based on atomic sites, the layer based counting can provide important physical insights to oxides composed of transition metal elements with multiple charge states and complex oxygen vacancy channels. With this new scheme, we successfully investigated surface formation energy and reconstructions on the phase change in the study of SrCoO2.5 and HSrCoO2.5 thin films and discovered that surface defects play important roles during the phase change and the change of magnetic order. In addition, we apply this new scheme to investigate the surface and interface stabilities in the interesting phase change phenomenon on the chemical reduction from VO 2 and V 2 O 3 , induced by the surface electron beam illumination. We find that the intrinsically different oxygen vacancy formation energy between these facets is a crucial factor. Additionally, we build an interface models and find that the interface stability of different facets and collective motions of O atoms near interface also significantly related to the phase transition. The research works are based on the following literature we have published in recent years.

Yupu Wang, Gaofeng Teng, Junyi Zhu*, “Surface Stability Analysis with H Adsorption Affected the Magnetic Fluctuation of Brownmillerite SrCoO2.5 Based on the Electron Counting Model by Layers” Journal of Phys. Chem. C 2022, 126, 29, 12251–12263

Zhang, Y., Wang, Y., Wu, Y., Junyi Zhu*, Pu Yu et al. “Artificially controlled nanoscale chemical reduction in VO 2  through electron beam illumination.” Nat Commun 14, 4012 (2023).