Revealing H-bonding interactions of 2D ice on Au(111)

Using density functional theory calculations, we provided clear evidence for the covalent and electrostatic nature of rich H-bonds in the 2D ice. Interestingly, we find that all H-bonds consistently populate several different principal states with both the bonding and antibonding features. However, the symmetric and asymmetric Hbonded cycles respectively show preferential HOMO-1 (3a1) and HOMO-2 (1b2) contributions to the H-bonding states. For all H-bonding types, alternating positive and negative regions on the second order serve as the direct evidences for the H-bonding electrostatics. Our investigations advance our understanding of the H-bonding nature of rich H-bonds in the ice.