Ammonium carbonates, sensu lato, have relevance to carbon capture schemes and as potential hydrogen storage materials. These compounds occur on Earth as minerals and, since ammonia is thought to exist on icy planetary bodies, as 'rock-forming' minerals in the colder reaches of the solar system. Surprisingly little work on the structures and properties of these materials has been done; such work is essential for accurate modelling of icy planetary interiors. Having done high-pressure work on ammonium bicarbonate, and complementary DFT studies, this work aims to characterise to high precision the structure, thermal expansion and vibrational spectroscopy of ammonium bicarbonate using HRPD.