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Alloying Effect Study on Thermodynamic Stability of MgH2 by First-principles Calculation
Zhen-zhen Wan1, Zhong-min Wang1,2, Dian-hui Wang1, Yan Zhong1,2, Jian-qiu Deng1, Huai-ying Zhou1, Chao-hao Hu1
1.School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, China;2.Guangxi Experiment Center of Information Science, Guilin 541004, China
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1, 王仲民1,2, 王殿辉1, 钟燕1,2, 邓健秋1, 周怀营1, 胡朝浩1
1.桂林电子科技大学材料科学与工程学院, 桂林 541004;2.广西信息科学实验中心, 桂林 541004
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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