The Icosahedral (H$_2)_{13}$ Supermolecule

TL;DR

This paper explores the formation and stability of icosahedral (H2)13 supermolecules in various compounds, using ab initio simulations to predict their properties and potential for hydrogen storage.

Contribution

It introduces the concept of icosahedral (H2)13 supermolecules in multiple compounds and predicts their stability and phase transitions through ab initio molecular dynamics.

Findings

(H2)13 supermolecules are stable in several hydrogen compounds.

Predicted phase transition at low temperature.

Supermolecule structure is consistent across different compounds.

Abstract

We investigate a range of possible materials containing the supermolecular form of hydrogen comprising 13 hydrogen molecules arranged in an icosahedral arrangement. This supermolecule consists of freely rotating 12 hydrogen molecules in an icosahedral arrangement, enclosing another freely rotating molecule. To date, this supermolecule has only been observed in a compound with Iodane (HI). The extremely high hydrogen content suggests possible application in hydrogen storage so we examine the possibility of supermolecule formation at ambient pressures. We show that ab initio molecular dynamics calculations give a good description of the known properties of the HI(H2)13 material, and make predictions of the existence of related compounds Xe(H2)1, HBr(H2)13 and HCl(H2)13, including a symmetry-breaking phase transition at low temperature. The icosahedral (H2)13 supermolecule, remains stable in all these compounds. This suggests (H2)13 is a widespread feature in hydrogen compounds, and that appropriately-sized cavities could hold hydrogen supermolecules even at low pressure. The structure of the supermolecule network is shown to be independent of the compound at equivalent density.