The molecular dynamics in the crystal and the thermodynamic functions of the beta-polymorph of glycine have been determined from a combination of molecular translation-libration frequencies reflecting the temperature dependence of atomic displacement parameters (ADPs), with frequencies derived from ONIOM(DFT:PM3) calculations on a 15-molecule beta-glycine cluster. ADPs have been obtained from variable-temperature diffraction data to 0.5 angstrom resolution collected with X-ray synchrotron (10-300 K) and sealed tube radiation (50-298 K). At the higher temperatures, the ADPs of beta-glycine from synchrotron are larger than those from sealed tube probably due to different experimental conditions. The lattice vibration frequencies from normal-mode analysis of ADPs and the internal vibration frequencies from ONIOM(B3LYP/6-311+G(2d,p):PM3) calculations agree with those from spectroscopy. Estimation of thermodynamic functions using the vibrational frequencies, the Einstein and Debye models of heat capacity, and the room-temperature compressibility provides C-p, H-vib, and S-vib that agree with those from calorimetry. The beta-phase with higher H and G is found to be less stable than the alpha-phase in the temperature range of the experiment.