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

► Vibrational spectrum of an adsorbed molecule is computed. ► Anharmonic frequencies are obtained without a potential surface. ► Vibrational Schrödinger equation is solved in a small, adaptable basis. ► A general algorithm is proposed that can be used in surface science labs.