Berlinsky, A. JohnHarris, A. Brooks2023-05-232023-05-231978-06-122015-08-13https://repository.upenn.edu/handle/20.500.14332/43208A mean-field theory for the ordering of hydrogen molecules on a triangular net is derived in terms of the quadrupole coupling constant Γ, the crystal field Vc, and the temperature T. The phase diagram consists of six regions, separated by first- and second-order transitions. For almost all values of Vc/Γ for which ordering occurs, the disordered to ordered phase transition is continuous. At T=0 K, all phases have energy gaps except for a ferrorotational phase which behaves like an XY model.PhysicsArticle