Density-functional study of the hydrogen-bonded water cluster H5O2+

Abstract

We study the H5O2+ molecule as a basic unit of the proton transfer in hydrogen-bonded water networks in density-functional theory (DFT) scheme using the finite-difference pseudopotential method. The comparison of dissociation energies obtained from the local-density approximation (LDA) and the generalized-gradient approximation (GGA) with experimental results and other accurate quantum chemistry calculations shows that (1) the GGA in DFT is a reliable scheme for this system, and (2) we can obtain the effect of including higher correlation by using the GGA over the LDA. We also address the technical issue of implementing the GGA exchange-correlation potential in the real space.