Structural study of the ferroelectric instability in Sn2P2Se6 R. Enjalbert, J. Galy, Y. Vysochanskii, A. Ouédraogo and P. Saint-Grégoire Eur. Phys. J. B, 8 2 (1999) 169-177 Published online: 15 March 1999 DOI: 10.1007/s100510050680