Enhancement of T(c) in the atomic phase of iodine-doped hydrogen at high pressures.The high-pressure structures and superconductivity of iodine-doped hydrogen have been studied by ab initio calculations. 
ab initio calculations
Above 100 GPa, we discover a stable phase with Pnma symmetry in the H2I stoichiometry that consists of a monatomic iodine tube trapping hydrogen molecular units. 
Pnma symmetry
Interestingly, H2 molecular units dissociate and form a novel atomic phase with R3̄m symmetry at 246 GPa. 
R3̄m symmetry