FeLi[PO4]: Dissection of a Crystal Structure - Inorganic 3D Structures - page 85

Table 1 The unit cell dimensions and interatomic distances of some of the substructures existing
in the two phases of FeLi[PO 4 ]
Compound Unit cell ( ˚ ) d(Fe-Fe) ( ˚ ) d( C -LiCl)

d(LiCl)

Figures

fcc-Fe a ¼ 3.65 2.58

a ¼ 3.67
c ¼ 5.04

FeS (PbO type) 2.61 11a, b

FeLiP ( C -FeS)

a ¼ 3.69
c

2.61 11c

¼ 6.02

FeLiP ( C -LiCl) a ¼ 5.22 2.61 2.61, 2.89, 3.13 11d, e

c 6.02

mean a

¼

¼ 5.49

LiCl 5.14 2.57

a b

c d e

Fig. 11 (a) The PbO-type structure of FeS showing the tetra-connectivity of both Fe and S atoms.
(b) The Fe subnet of FeS showing the 4 4 planar nets formed by the Fe atoms. They are equal to the
(1 0 0) planes of fcc -Fe. (c) Perspective view of the structure of the Zintl phase FeLiP, showing that
the -FeS subarray is identical to the FeS represented in (a). (d) The 4 4 planar nets formed by the

Fe atoms in FeLiP. They coincide in topology and dimensions with those of (b). (e) The LiP
subarray in FeLiP. It can be considered as a

C

C -LiCl structure (rocksalt) where alternate layers of

cubes are occupied by the Fe atoms

In this section, we will focus on the structure of tetragonal FeS, represented in
Fig. 11a . It can be considered as a (II)-(VI) compound, adopting consequently a
four-connected such as PbO type in which both atomic species are four-connected,
like in the Group 14 structures. Recall the [AlSi] 1 subarray in the Zintl phase
NaAlSi [ 28 ] (Fig. 8f ).