The electric field dependence of vibrational frequency of H atoms on Pt electrodes was investigated by performing DFT calculations for the Pt-13 cluster with an adsorbed atop H atom under external fields. Calculations with and without the solvent effect depending on dielectric constant showed that the external field, which was significantly enhanced by the solvent effect, affects Pt H stretching frequency by causing electron transfer between the Pt-H bond and the cluster. Our results agree semi-quantitatively with the large Pt-H frequency change observed experimentally and can be systematically explained in terms of the effective field around the Pt-H bond. (c) 2007 Elsevier B.V. All rights reserved.