The structure of room-temperature ZrP2O7 is shown to be orthorhombic by a combination of high-resolution synchrotron powder diffraction and single-crystal synchrotron diffraction data. Small nontwinned single crystals were obtained by synthesizing the compound using solvothermal methods at temperatures below the cubic to orthorhombic phase transition. The average P - O - P angle is 146 degrees. DFT calculations ( B3LYP/ AUG-cc-pVDZ) on the isolated P2O74- anion yield a P - O - P angle of 153.42 degrees and indicate that the barrier to inversion is of the order 3.6 kJ mol(-1).