Figure 3
M—O2 distances as functions of t′ (= −σ2x2 + x4). Solid and dotted lines represent modulated and unmodulated structures, respectively. Mi, O2i and O2ii atoms correspond to those in Fig. 2. Symmetry operations are (i) x1, x2, x3, x4; (ii) x1 + ½, x2 + ½, x3, x4 + ½. |