The electric fields enhance the non-covalent intermolecular interaction between H2 and (MgO)3

The hydrogen storage properties of (MgO)(3) cluster under an electric field are investigated by M06-2X method. The results show that H-2 can be adsorbed on a Mg or O atom through non-covalent intermolecular interaction, and applying an external electric field can effectively improve the non-covalent interaction. The non-covalent interaction is characterized by electronic structures analysis. The mechanisms for the enhancement of adsorption are discussed. When H-2 is adsorbed on Mg atom, on one hand, the electric field facilitate the charge transfer from H-2 to cluster, strengthening their electrostatic interaction. On the other hand, there also forms weak orbital interaction, further enhancing the adsorption. While H-2 adsorption on O atom, the electric field promotes not only the electrostatic but also the dispersion interaction due to the polarization effect. Moreover, the hydrogen storage mass density reaches 16.7 wt%, suggesting that (MgO)(3) is a potential hydrogen storage material under an electric field.