A quantitative assessment of the accuracy of centroid molecular dynamics for the calculation of the infrared spectrum of liquid water.

A detailed analysis of the infrared lineshapes corresponding to the intramolecular bond vibrations of HOD in either H(2)O or D(2)O is presented here in order to quantitatively assess the accuracy of centroid molecular dynamics in reproducing the correct features of the infrared spectrum of water at ambient conditions. Through a direct comparison with the results obtained from mixed quantum-classical calculations, it is shown that centroid molecular dynamics provides accurate vibrational shifts and lineshapes when the intramolecular bond stretching vibrations are described by a physically reasonable anharmonic potential. Artificially large redshifts due to a so-called "curvature problem" are instead obtained with an unphysical shifted harmonic potential because the latter allows substantial probability density at zero bond lengths.