Figure 3.4.2.5

Janovec, V.; Přívratská

doi:10.1107/97809553602060000645

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

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International Tables for Crystallography (2006). Vol. D. ch. 3.4, p. 469

Figure 3.4.2.5

V. Janovec^a ^* and J. Přívratská^b

^a Department of Physics, Technical University of Liberec, Hálkova 6, 461 17 Liberec 1, Czech Republic, and ^bDepartment of Mathematics and Didactics of Mathematics, Technical University of Liberec, Hálkova 6, 461 17 Liberec 1, Czech Republic
Correspondence e-mail: janovec@fzu.cz

Figure 3.4.2.5

Four basic single-domain states $[{{\sf S}_1}\equiv 1_1]$ , $[{{\sf S}_2}\equiv 1_2]$ , $[{{\sf S}_3}\equiv 2_1]$ , $[{{\sf S}_4}\equiv 2_2 ]$ of the ferroic phase of a calomel (Hg₂Cl₂) crystal. Full $[\bullet]$ and empty $[\circ]$ circles represent centres of gravity of Hg₂Cl₂ molecules at the levels [z=0] and [z=c/2] , respectively, projected onto the [z=0] plane. The parent tetragonal phase is depicted in the centre of the figure with a full square representing the primitive unit cell. Arrows are exaggerated spontaneous shifts of molecules in the ferroic phase. Dotted squares depict conventional unit cells of the orthorhombic basic domain states in the parent clamping approximation. If the parent clamping approximation is lifted, these unit cells would be represented by rectangles elongated parallel to the arrows.