Encouraged by our success with -TMA, we applied CSP to explore the space of possible crystal structures of ADTA. The known, dense crystal structure of ADTA features double hydrogen bonds at each carboxylic acid group (Figure ) and close packing is achieved via 5fold interpenetration of the resulting diamondoid networks. A group of predicted crystal structures at the global minimum of the CSP landscape (Figure ) contain this 5-fold interpenetrated diamondoid hydrogen bonding. One of these predicted structures, 5.6 kJ/mol above the global minimum, reproduces the known crystal structure accurately (Figure ), with a root mean squared deviation in atomic positions of 0.28 Å within a cluster of 20 molecules taken from the observed and predicted crystal structures (Table , Figure ).