主讲人：Penghao Xiao 助理教授 加拿大哈利法克斯达尔豪斯大学

题   目：Atomistic processes driven by electric field/voltage --three levels of theory

日   期：2024年6月21日     时   间：15:00-16：00

地   点：哈尔滨工业大学（深圳）, 信息楼L-213

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摘   要：While atoms in motion are difficult to be observed directly in experiments, their behaviors can be understood through the lens of computation. In this talk, I will discuss our recent progresses on simulating atomistic processes under electric field/voltage from first principles. Timescale of milliseconds and beyond could be reached, allowing direct comparison with experiments. Three examples will be discussed:

1. Dislocation motion in ZnS entirely driven by electric field. I will discuss how to incorporate the effect of electric field in barrier calculation under the first-order approximation. Density functional theory calculation shows the dislocation is charged and electric field lowers its moving barrier.

2. Charge/discharge kinetics in LiNiO2, a Li-ion battery cathode material. High-Ni layered oxide cathodes have high energy density but exhibit profound capacity loss after cycling. The underlying mechanisms have not been well understood, hampering further improvements of these materials. Using LiNiO2 as a model system, our atomistic simulations successfully reproduce the first-cycle irreversible capacity loss at the end of discharge. Also, we find the rate-limiting step switches from diffusion to H2-H3 phase transition at the end of charge. After cycling, the formation of a surface densified phase suppresses the H3 phase nucleation, dramatically impeding the delithiation process when Li content is below 25%. These findings align well with recent experiments.

3. Exact saddle point search under constant voltage. Here, the number of electrons is automatically adjusted to the voltage, and the electric field is not necessarily uniform. Two charge transfer mechanisms of oxygen evolution reaction (OER) on RuO2 are compared.

报告人简介：肖鹏昊博士是加拿大哈利法克斯达尔豪斯大学（Dalhousie University）物理与大气科学系的助理教授。在 2021 年加入达尔豪斯大学之前，肖博士从德克萨斯大学奥斯汀分校获得博士学位，先后在劳伦斯伯克利国家实验室和劳伦斯利弗莫尔国家实验室进行博士后研究。他的团队专注于材料的计算研究，特别关注决定材料合成、性能和老化的动力学过程。通常结合密度泛函理论、过渡态理论、团簇扩展和动力学蒙特卡罗来模拟材料在实验相关时间尺度上的演变。应用领域包括电池、结构合金和电催化剂。他已发表 59 篇同行评审论文，总引用量 5100 余次。