Variationally Calculated Vibrational Energy Levels of Ammonia Adsorbed on a Ni(111) Surface

We have calculated vibrational energy levels for in ammonia molecule adsorbed oil a Ni(111) Surface. An exact kinetic energy operator for the gas phase molecule is combined with a potential energy function that is Calculated with the plane-wave density-functional theory. The resulting eigenvalue problem is solved variationally. The vibrational energy levels for a gas phase molecule are also calculated. The Calculated adsorption-related shift is + 193 cm(-1) for the symmetric bend, -54 cm(-1) for the asymmetric bend, -68 cm(-1) for the symmetric stretch, and -63 cm(-1) for the asymmetric stretch, in good agreement with the experimental values +190, -47, -67, and -84 cm(-1), respectively.