Fig xA Side view of the whole crystal structure
The Ga–O bond distances in Sr5Ga6O14 vary between 1.804 and 1.894 Å (Table 3b). They are in the normal range of oxogallate structures. Concerning the spread of individual Ga–O distances it Torin 2 can be noticed that the quaternary (Q4) tetrahedra around Ga(1) sharing all four oxygen ligands with neighboring tetrahedra are the least distorted ones. In general, the bond-valence sums for the different crystallographic sites showed satisfactory agreement with the expected values (see Table 3b). However, larger deviations occur for the oxygen atoms O(6) (BVS=1.659 v.u.) and O(5) (BVS=2.287 v.u.), respectively. This pronounced under- and overbonding at ambient pressure reflects a steric strain in the crystal structure of Sr5Ga6O14 and may be the explanation why high pressure is food pyramid needed for its preparation. Linkage between adjacent tetrahedral layers as well as charge compensation is provided by three symmetrically independent strontium ions which are surrounded by six to eight oxygen atoms. A side view of the whole crystal structure is presented in Fig. 8.