Hexagonal subcell

Phase 1 has a two-layer unit cell for the hydroxide component. In the (100) projection (in which the structural calculations were performed) the two idealised hydroxide layers (F in Fig. 5) have a relative rotation of 22° (98°), so that they may be related by an a-glide plane parallel to [010] of the sulphide component and perpendicular to the layers, or by a two-fold axis parallel to [010] of the sulphide component. The ortho-hexagonal subcells of the idealised hydroxide layers can be defined as mutually rotated by 98°, and they will be rotated by 41° and 139° from the component unit cell of the sulphide layers. Thus, the two hydroxide layers have the same orientation to the sulphide component (and to the common modulation), but the cell geometry assumed by Organova et al. makes them non-equivalent (Table 3). The published diffraction pattern suggests that the structure is of the SC type (or perhaps SI), modulated in the b direction. The close relationship with the tochilinites is apparent from the mutual orientation of the adjacent hydroxide and sulphide layers the deviation from that in tochilinites is only 4°. However, in tochilinites successive hydroxide layers are parallel. 

It has been reported extensively that fats solidify in more than one crystalline type (2-23). Triglycerides exhibit three main crystal types—ot, p, and p—with increasing degrees of stability and melting point. The molecular conformations and packings in the crystal of each polymorph have been reported. In the ot form, the fatty acid chain axes of the triglyceride are randomly oriented and the ot form reveals a freedom of molecular motion with the most loosely packed hexagonal subcell structure. 

Intermediate pseudohexagonal states between the chain geometry of the orthorhombic subcell O i and the hexagonal subcell have also been observed. The structure of sodium dodecyl sulphate (Sundell, 1977) is one example. 

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