In an earlier high-pressure survey of the P,T phase diagram of deuterated ammonium carbonate, we observed changes in the neutron powder diffraction patterns that are consistent with a number (between 3 and 6) of polymorphic phase changes. However, data suitable for unambiguous indexing of the powder patterns was not collected and there is a large degree of uncertainty as to whether some of the datasets truly reflect different phases or simply highly anisotropic peaks shifts.Our goal is to revisit these phases and collect the requisite data at long d-spaces, and also collect in small enough increments to follow peaks shift, such that we may identify and index new phases with confidence and potentially solve their structures.