第一性原理计算Mg2 Ni氢化物的电子结构及其稳定性分析

First principles investigation of electronic structures and stabilities of Mg_2 Ni and its complex hydrides

对Mg2Ni及其氢化物的能量和电子结构进行了第一性原理计算,并对Mg2Ni低温氢化物和高温氢化物的稳定性进行了分析.结果发现:在Mg2Ni中,Mg与Ni存在较强的相互作用.H原子的加入使得Mg的价电子向Ni的3d轨道转移,并在Ni-3d轨道和Ni-4p轨道间形成了带隙.Ni-4s和H-1s电子之间的成键作用,使得Mg和Ni间相互作用减弱了;从LT-Mg2NiH4中去掉一个H原子比HT-Mg2NiH4中去掉一个H原子需要更多的能量,表明高温相有利于脱氢反应,而低温相更适合储氢反应.

irst-principle calculations are carried out to investigate the energies and the electronic structures of Mg2 Ni alloy and its high/low temperature hydrides. Results show that strong bonding interaction between Mg and Ni atoms exists in the Mg2 Ni alloy. With H inserted, the charge transfer occurs from Mg to Ni-3d, which gives rise to a band gap between Ni-3d and Ni-4p orbitals. The interaction between Mg and Ni in LT/HT-Mg2NiH4 hydrides is weakened due to the covalent bonding between Ni-4s and H-1s. Therefore, it neads more energy to remove tt atoms from LT-Mg2NiH4 than from HT- Mg2NiH4, indicating that HT-Mg2NiH4 is more suitable for de-hydrogenation reaction while the LT-Mg2 NiH4 is suitable lot hydrogenation reaction.