A transition in which the degree of order of the system changes. Three principal types
of disordering transitions may be distinguished: (i) positional disordering in a solid,
(ii) orientational disordering which may be static or dynamic and (iii) disordering
associated with electronic and nuclear spin states.
Examples:
-
The transition of
LiFeO2, with a tetragonal unit cell, in which the
Li+ and
Fe3+
cations are perfectly ordered on crystallographically non-equivalent octahedral sites
to cubic
LiFeO2 in which the
Li+ and
Fe3+ cations are distributed randomly over all the octahedral sites.
-
The transition of orthorhombic
KCN to cubic
KCN in which the
CN− ions become oriented in any of the eight [111] directions.
-
A superconducting transition
Source:
PAC, 1994, 66, 577
(Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations
1994))
on page 587
Cite as:
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by
A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).
XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic,
J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8.
https://doi.org/10.1351/goldbook.
