Most molecules and solids exhibit simple isotope effects associated with vibrational modes. In the harmonic limit the vibrational frequency scales with the inverse square root of the mass. Hence, replacing hydrogen with deuterium (D) should reduce the frequency by a factor of 1.414 = sqrt(2). However, significant anharmonicity or non-adiabatic (violations of Born-Oppenheimer?) effects can lead to very different effects.
An important case is that of hydrogen bonding. The graph below shows gamma = the ratio of the O-H stretch stretch frequency to the O-D frequency as a function of the O-H frequency. The latter is a measure of the H-bond strength and is directly correlated with the donor-acceptor distance. The graph is taken from this paper.PNAS paper.