  We report self-assembly and phase transition behavior of lower diamondoid
molecules and their primary derivatives using molecular dynamic (MD) simulation
and density functional theory (DFT) calculations. Two lower diamondoids
(adamantane and diamantane), three adamantane derivatives (amantadine,
memantine and rimantadine) and two artificial molecules (Adamantane+Na and
Diamantane+Na) are studied separately in 125-molecule simulation systems. We
performed DFT calculations to optimize their molecular geometries and obtain
atomic electronic charges for the corresponding MD simulation, by which we
obtained self-assembly structures and simulation trajectories for the seven
molecules. Radial distribution functions and structure factors studies showed
clear phase transitions for the seven molecules.
