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

© International Union of Crystallography 2006
International Tables for Crystallography (2006). Vol. D. ch. 3.1, p. 369

Figure 3.1.5.18 

J. F. Scottc*
[Figure 3.1.5.18]
Figure 3.1.5.18

Pressure dependence of the `soft' optical phonon branch Raman spectra in potassium dihydrogen phosphate (after Peercy, 1975b[link]), showing the displacive character of the phase transition [purely order–disorder phase transitions cannot exhibit propagating (underdamped) soft modes].