First-Principles Simulation of Anharmonic and Anisotropic Vibrations of Glycinate on Copper.

Molecular vibrations within a hydrogen-bonded network are expected to be significantly anharmonic and hence poorly described by conventional normal-mode analysis. Moreover, the rather flat potential energy landscapes experienced in such cases imply sampling of several local-energy minima, casting further doubt upon the standard methodology. Both difficulties may be overcome through first-principles molecular dynamics, used here to obtain vibrational spectra and thermal ellipsoids for glycinate adsorbed on copper. Vibrational anisotropy and signatures of hydrogen bonding are highlighted and discussed.