Calculating anharmonic vibrational frequencies of molecules adsorbed on surfaces directly from ab initio energies with a molecule-independent method: H2O on Pt(111)

We compute vibrational energy levels of a water molecule and shifts due adsorption on Pt(111). The calculations are done using a variation of a recently proposed algorithm that solves the vibrational Schrödinger equation and accounts for anharmonicity and coupling. A small set of adaptable basis functions is used to obtain the vibrational spectrum directly from ab initio data, obviating the need for an analytical potential energy function. The method is general and fast — all calculations were performed on a personal computer. It is a black-box and easily usable tool that will enable surface scientists to compute approximate spectra of adsorbed complexes without neglecting anharmonicity and coupling effects.