Total energy calculation is common in the field of materials science. However, in view of design for hydrogen storage materials, information is still limited about the role of each constituent element in them. In this paper, a unified approach based on the atomization energy concept is proposed for understanding the chemical bond in hydrides without using the standard concept of covalent and ionic bonds. The atomization energies, ΔEH for the hydrogen atom and ΔEM for the metal atom in each hydride, are evaluated using the energy density analysis of the total energy, and an ΔEH vs. ΔEM diagram is constructed. All the hydrides, including complex hydrides and metal hydrides, can be located on this diagram, although there are significant differences in the nature of the chemical bond among them. Also, for hydrocarbons, CmHn, the atomization energy for carbon, ΔEC, increases linearly with the ratio of carbon number to hydrogen number, m/n, while keeping ΔEH constant.
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