You predict hydrogen atoms can cluster independent of any matrix. I know of no evidence for the formation of hydrogen clusters outside of normal chemical interaction. If they should form, the conditions in the chemical structure must be very different from those normally present in a chemical system. A very rare and unusual condition must form first in which normal chemical behavior no longer applies.
The clustering of hydrogen atoms forms the basis of Holmlid'e ultra dense hydrogen technology. The process by which these clusters form is through the formation of Hole Superconductivity. The formation of this state is driven by the minimization of energy. Rossi has referenced this process in his last paper and states in chapter 4 that these hydrogen clusters are the key to his reaction.