Interactions between ortho-H2 molecules in nearly pure para-H2

A comprehensive theory is presented for the interaction of two ortho-H 2 molecules in otherwise pure solid para-H 2 . A general Hamiltonian is constructed, which takes full account of the local environment of the pair of ortho molecules. For the dominant interactions between the pair, the pair axis is an axis of cylindrical symmetry. The various parameters which describe these interactions are then calculated from a microscopic theory. …