Orientational glass explained

In solid-state physics, an orientational glass^[1] is a molecular solid in which crystalline long-range order coexists with quenched disorder in some rotational degree of freedom.

An orientational glass is either obtained by quenching a plastic crystal, (e.g. cyclohexane, levoglucosan^[2]), or it is a mixed crystal in which positional disorder causes additional disorder of molecular orientations, e.g. CN orientations in KCN:KBr.^[3]

Notes and References

1. Loidl . A. . Orientational Glasses . Annual Review of Physical Chemistry . Annual Reviews . 40 . 1 . 1989 . 0066-426X . 10.1146/annurev.pc.40.100189.000333 . 29–60. 1989ARPC...40...29L .
2. Moura Ramos . Joaquim J. . Diogo . Hermínio P. . Orientational glass, orientationally disordered crystal and crystalline polymorphism: A further study on the thermal behavior and molecular mobility in levoglucosan . Journal of Molecular Liquids . Elsevier BV . 286 . 2019 . 0167-7322 . 10.1016/j.molliq.2019.110914 . 110914. 164662415 .
3. Knorr . K . The Glasslike State of the Mixed Alkali Halide-Alkali Cyanides . Physica Scripta . IOP Publishing . T19B . 1987-01-01 . 0031-8949 . 10.1088/0031-8949/1987/t19b/034 . 531–536. 1987PhST...19..531K .