Unveiling structural, electronic properties and chemical bonding of (VH2)n (n=10–30) nanoclusters: DFT investigation

The geometries, electronic properties, and chemical bonding of (VH2)n (n=10-30) nanoclusters are systematically investigated by a combination of artificial bee colony optimization with density functional theory calculations. Structure analysis indicates that the structures of (VH2)n nanoclusters tend to be a disorder, where the hydrogen atoms prefer to occupy the hollow sites among different V atoms, binding three V atoms to form the HV3 moieties. The bond length suggests that the average V-V bond lengths are about 2.60 A, and the average V-H bond lengths are near 1.86 A, which close to the experimental values of 2.77 A and 1.79 A for the V-V and V-H of bulk vanadium hydride, respectively. Interestingly, the coordination numbers of V-H fluctuate around 5.50 in the nanoclusters, and the corresponding value of H-V is estimated at 3.00. Moreover, the electronic properties and chemical bonding analyses indicate that d orbitals of V atoms and s orbitals of H atoms have a relatively large overlap to form sigma bonds. Specifically, the σ molecular orbital of H2 can donate electronic density to the d orbital of V atom, exhibiting the Kubas interaction in V24H48 and V29H58 nanoclusters. Kubas interaction results in a longer bond between the hydrogen molecule and the V atom.