On the amphiphilic behavior of the hydrated proton: an ab initio molecular dynamics study

The ab initio atom-centered density matrix propagation (ADMP) method has been employed to study the dynamics of protonated water clusters of various sizes. An interesting result that hints at the possible amphiphilicity of the hydronium ion is detected. The hydrated proton tends to reside on the surface of the water clusters studied, with the lone pair on the protonated oxygen pointing "outwards" from the cluster. It is also noted that the hopping rate and average bonding topology in the local vicinity of the protonated species show a pronounced difference when treated with B3LYP and BLYP functionals. This is proposed to be on account of the potential for greater electronic exchange interactions in the vicinity of the positive charge. (C) 2004 Elsevier B.V. All rights reserved.