Hydrogen physisorption on the (BeO), BH(Be,Ti), and BTi metal clusters: a computational study of energies and atomic charges.

The equilibrium structures of BeO clusters and Be,Ti-decorated boranes were computed with the ωB97X-D method and the 6-31G + (2d,2p) and aug-cc-pVTZ basis sets to study their intermolecular interactions with hydrogen molecules. Thermochemical and molecular properties such as the harmonic vibrational frequency, dipole and quadrupole moments, and atomic charges are employed to understand the attractive interactions that control the adsorption process. Comparison of molecular properties and atomic charges of the studied compounds before and after H molecule adsorption shows that most of the interactions among the BeO clusters and boranes with H molecules constitute a combination of dispersion, electrostatic, and weak charge transfer interactions. Calculated values of Hirschfeld atomic charges and ΔE (in parenthesis) (BeO).8H (0.028 e and -2.0 kcal.mol), (BeO).12H (0.030 e and -2.8 kcal.mol), BTi.10H (0.045 e and -15.4 kcal.mol), and BTi.10H (0.058 e and -15.3 kcal.mol) show qualitative correlation between hydrogen atomic charges and electronic energy of hydrogen interaction. The ωB97X-D/6-31 + G(2d,2p) values of Gibbs free energy at 298.15 K for (BeO).8H BHTi.4H and BTi.10H clusters are equal to -5.0, -4.9, and -5.1 kcal.mol, respectively, which are within the range of energy parameters of materials that could be employed in hydrogen storage tanks for light vehicles.