摘要
Oxygen-containing rare-earth metal hydride YH_xO_y,is a newly found photochromic material showing fast photoresponse.While its preparation method,optical properties and structural features have been studied extensively,the photochromic mechanism in YH_xO_yremains unknown Here,using excited-state molecular dynamics simulation based on the recently developed real-time time-dependent density functional theory(RT-TDDFT)method,we study the photochemical reactions in YH_xO_y.We find that under photoexcitation,dihydrogen defects are formed within 100 fs.The dihydrogen defect behaves as a shallow donor and renders the material strongly n-type doped,which could be responsible for the photochromic effect observed in YH_xO_y.We also find that oxygen concentration affects the metastability of the dihydrogen species,meaning that the energy barrier for the dihydrogen to dissociate is related to the oxygen concentration The highest barrier of 0.28 eV is found in our model with O/Y=1:8.If the oxygen concentration is too low,the dihydrogen will quickly dissociate when the excitation is turned off.If the oxygen concentration is too high,the dihydrogen dissociates even when the excitation is still on.
含氧稀土金属氢化物YH_xO_y是一种新发现的、具有快速光响应的光致变色材料.尽管其制备方法、光学性质和结构特征已被广泛研究,但YH_xO_y中的光致变色机理仍然未知.本文采用基于最新开发的含时密度泛函理论的激发态分子动力学模拟研究了YH_xO_y中的光化学反应.结果发现,光激发下在100 fs内可以形成一种双氢缺陷.该双氢缺陷为浅施主,使材料表现出强n型掺杂行为,这可能是导致YH_xO_y中光致变色效应的原因.此外还发现,氧浓度会影响双氢缺陷的稳定性,这意味着双氢解离的能垒与氧浓度有关.在此模型中,当O/Y=1:8时,双氢解离的能垒约为0.28 eV.若氧浓度过低,在关闭激发时双氢会迅速解离;若氧浓度过高,即使在光激发下双氢也会快速解离.
作者
Jun Chai
Zewei Shao
Han Wang
Chen Ming
Wanseok Oh
Tang Ye
Yong Zhang
Xun Cao
Ping Jin
Shengbai Zhang
Yi-Yang Sun
柴骏;邵泽伟;王涵;明辰;Wanseok Oh;叶唐;张勇;曹逊;金平实;张绳百;孙宜阳(State Key Laboratory of High Performance Ceramics and Superfine Microstructure,Shanghai Institute of Ceramics,Chinese Academy of Sciences,Shanghai 201899,China;University of Chinese Academy of Sciences,Beijing 100049,China;Chemical Sciences Division,Lawrence Berkeley National Laboratory,Berkeley,California 94720,USA;Department of Electrical and Computer Engineering,University of North Carolina at Charlotte,Charlotte,North Carolina 28223,USA;Department of Physics,Applied Physics,and Astronomy,Rensselaer Polytechnic Institute,Troy,New York 12180,USA)
基金
the support by the National Natural Science Foundation of China(11774365)。
