影響及其微觀機(jī)理
(1. 長(zhǎng)沙理工大學(xué) 汽車(chē)與機(jī)械工程學(xué)院，長(zhǎng)沙 410114；
2. 湖南大學(xué) 材料科學(xué)與工程學(xué)院，長(zhǎng)沙410082；
3. 湖南大學(xué) 汽車(chē)車(chē)身先進(jìn)設(shè)計(jì)制造國(guó)家重點(diǎn)實(shí)驗(yàn)室，長(zhǎng)沙 410082)
摘 要: 采用第一性原理贗勢(shì)平面波方法，研究元素Al和Ti摻雜對(duì)Mg2Ni儲(chǔ)氫合金相結(jié)構(gòu)穩(wěn)定性的影響及其微觀機(jī)理。結(jié)果顯示：在摻雜濃度x=0~0.5范圍內(nèi)，所形成的Mg2Ni型Mg2-xMxNi(M=Al, Ti)固溶體合金的相結(jié)構(gòu)穩(wěn)定性隨Al摻雜濃度的增大而增強(qiáng)，隨Ti摻雜濃度的增大而減弱，且Mg2-xMxNi(M=Al, Ti)固溶體合金相對(duì)于立方結(jié)構(gòu)的Mg3MNi2(M=Al, Ti)化合物呈現(xiàn)熱力學(xué)不穩(wěn)定性，極易分解成由立方結(jié)構(gòu)Mg3MNi2(M=Al, Ti)和六方結(jié)構(gòu)Mg2Ni組成的復(fù)合相，計(jì)算結(jié)果與實(shí)驗(yàn)結(jié)果吻合。電子結(jié)構(gòu)分析表明，Al、Ti摻雜Mg2Ni儲(chǔ)氫合金的相結(jié)構(gòu)穩(wěn)定性與體系在低能級(jí)區(qū)的成鍵電子數(shù)密切相關(guān)。
關(guān)鍵字: Mg2Ni；儲(chǔ)氫合金；相結(jié)構(gòu)穩(wěn)定性；贗勢(shì)平面波；電子結(jié)構(gòu)
phase structural stability of Mg2Ni alloy
（1. Institute of Automobile and Mechanical Engineering,
Changsha University of Science and Technology, Changsha 410114, China;
2. College of Materials Science and Engineering, Hunan University, Changsha 410082, China;
3. State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body,
Hunan University, Changsha 410082, China）
Abstract:The influence and micromechanism of Al or Ti doping on the phase structural stability of Mg2Ni hydrogen storage alloy were investigated by the first-principles pseudopotential plane-wave method. The results show that within the range of doping concentration x from 0 to 0.5, the phase structural stability of Mg2Ni-type Mg2−xMxNi(M=Al, Ti) solid solution alloys is improved with increasing Al concentration. By contrast, the stability is weakened with increasing Ti concentration. These solid solution alloys all exhibit thermal instability with respect to the cubic Mg3MNi2(M=Al, Ti) compounds. They are likely to decompose into the multi-phases as composed of cubic Mg3MNi2(M=Al, Ti) and hexagonal Mg2Ni, which are in good agreement with the experimental results. The analysis of electronic structures shows that the phase structural stability of Mg2Ni hydrogen storage alloy with Al or Ti doping is closely associated with the bonding electron number of the doping systems, which originate mainly from lower energy ranges below Fermi energy level.
Key words: Mg2Ni; hydrogen storage alloy; phase structural stability; pseudopotential plane-wave; electronic structure
