(廣西大學(xué) 物理科學(xué)與工程技術(shù)學(xué)院，教育部有色金屬材料及其加工新技術(shù)重點(diǎn)實(shí)驗(yàn)室，南寧 530004)
摘 要: 采用基于密度泛函理論的第一原理贗勢(shì)平面波方法，對(duì)貯氫合金LaNi5及LaNi5(111)表面的電子結(jié)構(gòu)進(jìn)行計(jì)算，對(duì)H原子在LaNi5(111)表面吸附模型進(jìn)行構(gòu)型優(yōu)化。結(jié)果表明：LaNi5(111)表面馳豫結(jié)構(gòu)La原子向外凸出，Ni原子向里收縮，凹凸不平的表面層增加表面原子與H原子的接觸面積，表面層的有效體積約增大2.3%，有利于H原子向塊體內(nèi)擴(kuò)散；表面層有凈余的0.5個(gè)電子，有利于表面層上的電子轉(zhuǎn)移到H原子上；H2分子解離成兩個(gè)H原子后在LaNi5(111)表面的平衡穩(wěn)定結(jié)構(gòu)與氫化物L(fēng)aNi5H7晶體相同位置的結(jié)構(gòu)極為相似；闡述H2分子在LaNi5(111)表面的解離吸附機(jī)理，其反應(yīng)活化能約為0.27 eV。
關(guān)鍵字: LaNi5；電子結(jié)構(gòu)；吸氫機(jī)理；第一性原理
（Key Laboratory of National Education Ministry for Nonferrous Metals and Materials Processing Technology, College of Physics Science and Technology, Guangxi University, Nanning 530004, China）
Abstract:The electronic structures of LaNi5 hydrogen storage alloy and LaNi5(111) surface with hydrogen atoms were calculated by plane wave pseudo-potential method based on density functional theory. The results show that on the relaxed surface, La atoms protrude from surface and Ni atoms cave in, which enlarges the contacting area with H atoms. The effective volume of the surface layer is increased by 2.3%, which favors H atoms to diffuse into bulk from the surface. Calculated charge population presents negative charge on the surface, and the negative charge may transfer from the surface layer to H atoms. The stable structure by geometry optimizing after H2 molecule is dissociated into two H atoms on LaNi5(111) surface presents similar structure with hydride LaNi5H7 at the same position. The possible dissociation path and the mechanism of hydrogen-adsorbed are investigated with transition state method, and the activation energy of reaction is estimated as 0.27 eV.
Key words: LaNi5; electronic structure; hydrogen adsorption mechanism; first principle
