Structural, electronic and energetic properties of water adsorbed on β-Si_3N_4 (0001) surface: First-principles calculations

摘要

Structural, energetic and electronic properties of water molecules adsorbed on β-Si_3N_4 (0001) surface, at various coverages, are investigated using density functional theory. At low coverages (0 ≤ 0.5), it is found that all H_2O molecules undergo spontaneous dissociation forming hydroxyl (OH) and imino (NH) groups where the reactive sites are identified, a result shown for the first time using ab initio theory. For higher coverages (0 > 0.5), only partial dissociation takes place where some of the molecules stay intact being bound via H-bond in good agreement with experimental findings. The driving force for the water dissociation has been identified to be dangling bonds on lower coordinated N and Si surface atoms showing that not all surface atoms are reactive corroborating with previous experimental findings.