Preferred Label : commensurate–incommensurate transition;
IUPAC definition : A transition between two states having magnetic or crystallographic structures with
a basic lattice and an imposed super-periodicity. In the commensurate (lock-in) state
this super-periodicity is a simple rational multiple of the basic unit cell. In the
incommensurate state the ratio of the super-periodicity repeat distance to the basic
lattice repeat distance is irrational and may show continuous variation with variation
in some degree of freedom (e.g. temperature, pressure, composition) of the system.
Example: The transition of Rb sub 2 /sub ZnCl sub 4 /sub from an incommensurate structure
to a commensurate structure at the lock-in temperature, TL, which is dependent on
the crystal growth method and varies in the range 128 K to 190 K.;
Scope note : a commensurate–incommensurate transition also occurs in liquid-crystal systems where
there is an incommensurability in the packing of dimers in relation to monomers.;
Origin ID : C01189;
See also
A transition between two states having magnetic or crystallographic structures with
a basic lattice and an imposed super-periodicity. In the commensurate (lock-in) state
this super-periodicity is a simple rational multiple of the basic unit cell. In the
incommensurate state the ratio of the super-periodicity repeat distance to the basic
lattice repeat distance is irrational and may show continuous variation with variation
in some degree of freedom (e.g. temperature, pressure, composition) of the system.
Example: The transition of Rb sub 2 /sub ZnCl sub 4 /sub from an incommensurate structure
to a commensurate structure at the lock-in temperature, TL, which is dependent on
the crystal growth method and varies in the range 128 K to 190 K.
