A non-interpenetrated diamondoid crystal structure is also found among the predicted structures, along the same roughly linear energy-density relationship as the lowest energy 2-fold, 3-fold, 4-fold and 5-fold interpenetrated forms. This non-interpenetrated structure, 78.6 kJ/mol above the global minimum 5-fold network, has a density of 0.324 g/cm , in excellent agreement with the structure hypothesized by Ermer. However, the CSP results show that, at these low densities, there are many energetically preferable structures with similar densities and different hydrogen bonding. The presence of alternative, lower energy structures in this density region suggests that the highly porous, non-interpenetrated structure is too unstable, so is unlikely to be observed. Moreover, even if it could be formed as a solvated structure, its position on the CSP landscape suggests that it might not occupy a sufficiently deep, isolated energy basin to be kinetically stable as an unsolvated structure.