International
Tables for
Crystallography
Volume D
Physical properties of crystals
Edited by A. Authier

International Tables for Crystallography (2006). Vol. D. ch. 3.1, p. 370

Figure 3.1.5.22 

J. F. Scottc*
[Figure 3.1.5.22]
Figure 3.1.5.22

Phase diagram for sodium nitrite for electric fields applied perpendicular to the polar b axis. In this situation, a Lifshitz point is possible where phase boundaries `kiss' (touch tangentially).