Polyhedral tilting

Rare earth manganites, LnMn03 (Ln = rare earth) polyhedral tilting and spiral magnetic ordering... 

Table 3. Polyhedral bulk modulus for Tl, T2, Ml, M2 and interlayer sites, in kbar. Axial and volume compressibilities (fia,b,c,v) ir kbari, and first derivative versus P of p/Po, in kbar . Bulk modulus at P = 0 (ATo, in kbar) calculated by the Birch-Mumaghan EoS, constraining its first derivative versus P (K o) to be equal to 4. Tetrahedral rotation angle (a) and tetrahedral tilting (Az) first derivative versus P, in °kbar and Akbar % respectively.

TEM and synchrotron XRD results have revealed that the Li3MC03P04 structure transforms from monoclinic to triclinic after ion exchange [89, 92]. Ah initio computations have also shown that the lowest energy stmcture of the Li compound is approximately the same as its Na precursor, as shown in Fig. 18. In the Li compound, the polyhedral are slightly turned and tilted so that the 2-fold axis and mirror plane present in the P2i/m space group are lost and only the inversion symmetry is preserved, giving the computed cell PI symmetry. 

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