Hydrogen adsorption on two-dimensional germanene and its structural defects: an ab initio investigation.

Herein, the adsorption of hydrogen on pristine germanene was studied using ab initio calculations. By performing a converged density functional theory calculation, we have found the nearly degenerate nature of hydrogen at the top sites HT1 and HT2, among which HT1 is the most stable site. The adsorption of a hydrogen atom on germanene led to local structural changes in germanene. To the best of our knowledge, this is the first study on the investigation of the localized surface curvature and zero-point energy of hydrogen for 2D germanene. Moreover, we demonstrated the properties of germanene defects via the four obtained defects: the Stone-Wales (55-77), divacancy (77-555-6), divacancy (555-7), and pentagon-heptagon linear (5-7) defect. The lowest formation energy of the pentagon-heptagon linear defect is shown for the first time in this study.