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Alloying Effect Study on Thermodynamic Stability of MgH2 by First-principles Calculation
Zhen-zhen Wan,Zhong-min Wang,Dian-hui Wang,Yan Zhong,Jian-qiu Deng,Huai-ying Zhou,Chao-hao Hu
Author NameAffiliationE-mail
Zhen-zhen Wan School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, China  
Zhong-min Wang School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, China;Guangxi Experiment Center of Information Science, Guilin 541004, China zmwang@guet.edu.cn 
Dian-hui Wang School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, China  
Yan Zhong School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, China;Guangxi Experiment Center of Information Science, Guilin 541004, China  
Jian-qiu Deng School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, China  
Huai-ying Zhou School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, China  
Chao-hao Hu School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, China chaohao.hu@guet.edu.cn 
Abstract:
First-principles calculations based on density functional theory were performed to study the effect of alloying on the thermodynamic stability of MgH2 hydride (rutile and fluorite structures) with transitional metals (TM=Sc, Ti, Y) and group IIA elements (M=Ca, Sr, Ba). The results indicate that fluorite structure of these hydrides are more stable than its relative rutile structure at low alloying content (less 20%), structural destabilization of MgH2 appears in the alloying cases of Ti, Sr and Ba respectively. The structure-transition point from rutile structure to fluorite structure is at around 20% for MgH2-TM, and about 40% for MgH2-M. The formation enthalpy of fluorite Mg0.5Ba0.52 is about 0.3 eV and higher than that of fluorite MgH2, indicating that its hydrogen-desorption temperature at atmospheric pressure will be much lower than that of pure MgH2. Good consistency between experimental and calculated data suggests that above-adopted method is useful to predict structural transition and properties of MgH2 based hydrides for hydrogen storage.
Key words:  MgH2  First-principles study  Alloying  Destabilization  Structural transition
FundProject:
基于第一性原理的合金化掺杂MgH2的热力学稳定性研究
万臻臻,王仲民,王殿辉,钟燕,邓健秋,周怀营,胡朝浩
摘要:
基于密度泛函的第一性原理,系统研究了合金化掺杂过渡金属(TM=Sc,Ti,Y)和IIA族元素(M=Ca,Sr,Ba)对MgH2(金红石和萤石结构)的热力学稳定性的影响。结果表明,在低掺杂量(<20%) 时,MgH2的萤石结构比金红石结构相对更稳定。掺杂Ti,Sr,Ba时,MgH2的结构发生了失稳现象。MgH2由金红石结构转变到萤石结构的掺杂TM和M的比例分别大约在20%和40%左右。Mg0.5Ba0.52萤石结构的形成焓比MgH2萤石结构高约0.3 eV,表明其放氢温度在标准大气压下将远低于纯MgH2。理论计算数据与实验数据有很好的一致性.
关键词:  MgH2  第一性原理  合金化  失稳  结构转变
DOI:10.1063/1674-0068/29/cjcp1602036
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