Structural, electronic and thermodynamic properties of Al- and Si-doped 伪-, 纬-, and 尾-MgH₂: Density functional and聽hybrid density functional calculations

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• 作者：Tuhina Adit Maark^a ; ^{tuhina.maark@physics.uu.se} ; Tanveer Hussain^a ; Rajeev Ahuja^a ; ^b
• 关键词：Hybrid density functionals ; Magnesium hydride ; Hydrogen storage ; Density of states
• 刊名：International Journal of Hydrogen Energy
• 出版年：2012
• 期刊代码：42_03603199
• 类别：ch
• 出版时间：June, 2012
• 卷：37
• 期：11
• 页码：9112-9122
• 文件大小：1415 K

摘要

In this work, we present a detailed study of Al- and Si-doped 伪-, 纬-, and 尾-MgH₂ phases using the gradient corrected density functional GGA-PBE and the hybrid Hartree-Fock density functionals PBE0 and HSE06 within the framework of generalized Kohn-Sham density functional theory (DFT) using a plane-wave basis set. We investigate the structural, electronic, and thermodynamical properties of these compounds with regard to their hydrogen storage effectiveness. PBE0 and HSE06 predict cell parameters and bond lengths that are in good agreement with the GGA-PBE calculations and previously known experimental results. As expected smaller band gaps (E_gs) are predicted by GGA-PBE for the pure magnesium hydride phases. PBE0 overcomes the deficiencies of DFT in treating these materials better than HSE06 and yields E_gs that compare even better with previous GW calculations. Both the hybrid functionals increase the E_gs of the Al-doped magnesium hydrides by much less magnitudes than of the Si-doped phases. This difference is interpreted in terms of charge density distributions. Best H₂ adsorption energies (螖H_ads) are computed by HSE06 while GGA-PBE significantly overestimates them. Si-doped 伪- and 尾-MgH₂ exhibited the least negative 螖H_ads in close proximity to the H₂ binding energy range of 鈭?.21 to 鈭?.41聽eV ideal for practical H₂ storage transportation applications.