DFT Study of H Adsorption on Magnesium-Doped Aluminum Clusters

In this study we use density functional theory (DFT) to investigate the properties and H adsorption characteristics of structural isomers of the magnesium-doped aluminum cluster, Al 12 Mg. Our results show that the exohedral structure ( exo -MgAl 12 ) is significantly lower in energy (1.59 eV) than the endohedral structure ( endo -Al 12 Mg); however, the exohedral structure shows significant structural distortion. Our calculations demonstrate that H binds favorably to both exohedral and endohedral structures. Generally, binding energies for H to both clusters range from ∼2.3 to 2.5 eV with atop positions slightly favored, except for addition directly to the exohedral Mg atom, where the binding energy drops to 1.92 eV. We include a DFT molecular dynamics study of the endo -Al 12 Mg and endo -Al 12 MgH clusters which revealed the isomerization to the respective exostructures at finite temperatures (100−600 K). Interestingly, hydrogen adsorption appears to enhance the isomerization.