Speaker
Prof.
Cheol Ho Choi
(Kyungpook National University)
Description
With the help of our QM/EFP scheme, the adsorptions of Na+, F-, Br- and Cl- ions on Ih ice surface were theoretically studied. Drastically different adsorption behaviors depending on ion signs and surface heterogeneity were observed. The positive Na+ ion forms 4 ~ 5 Na+-O interfacial bondings regardless of the numbers of hydrogen dangling bonds (HDB), yielding consistent adsorptions with large stabilization energies of -49.2 ~ -65.6 kcal/mol. On the other hand, the binding strengths of negative ions are sensitive to the numbers of HDB. In the particular binding sites where there is no HDB, both Cl- and Br- cannot form a stable surface adsorption product. At the same binding site, more reactive F- can undergo insertion reaction into surface hydrogen bonding. A molecular HF and a hydroxide is formed on a site with one HDB, showing that the surface acid-base chemistry may depend on the surface heterogeneity. In general, the versatile bonding ability of Na+ through s and empty p orbitals provides strong interactions with the ice surface by disrupting surface hydrogen bonding network, which in turn reduces its initial penetration barriers into bulk. However, the ice surface structures are intact in the case of negative ion adsorptions, making their penetrations into bulk difficult.
Significance statement
Detailed binding structures and characteristics of ions on ice surface.
Primary author
Prof.
Cheol Ho Choi
(Kyungpook National University)
