Chemistry Reference
In-Depth Information
¼ C
-
31
Ga, we obtain a pseudo-atom of the Group 13 (recall the bixbyite-type
structure of In
2
O
3
). Similarly, if we replace Li by Na, we get
39
[NaN
4
]
-
39
Y.
¼ C
4.3 Substructures in Space Group Fm
3
Table
14
shows the Barnighausen Tree for Case 4 above. As can be seen, there
are two b
ra
nches,
only one of which leads to the lattice sites of
b
-Li
7
VN
4
in space
group
a
3.
However, a search of the database in space group
P
m
3 reveals that for all the
structures reported, the sites 4
a
and 4
b
are occupied, implying the complete absence
of substructures of
b
-Li
7
VN
4
in this space group.
F
5 The Alpha Phase of Li
7
V
V
N
4
This polymorph, first identified by Niewa et al. [
6
], is tetragonal (
a
¼
6.757,
c
¼
4.882
˚
,V
222.92
˚
3
,S.G.
arnighausen
Tree” relating its space group to that of the anti-fluorite-type parent, Li
2
O. We show this
¼
P
4
2
/
nmc
), and these same authors derived the “B
€
5.1 Li
6
MoN
4
,Li
6
WN
4
,Li
6
ZnO
4
and Li
6
CoO
4
Other very similar compounds to
a
219.3
˚
3
and
anti-fluorite-type superstructures. We note, however, that Li
7
NbN
4
and Li
6
MoN
4
are isoelectronic, as are Li
7
TaN
4
and Li
6
WN
4
. Moreover, early work by Juza et al
.
isoelectronic with Li
7
VN
4
.
Li
7
VN
4
is then simply a Li-stuffed Li
6
CrN
4
structure. In terms of the
EZKC
, one
Li atom donates one electron to V to give
C
-Cr, resulting in the compound Li
6
(
4.925
˚
,
V
¼
6.673,
c
¼
¼
-Cr)N
4
. In the same way, if we take our parent compound as Li
7
NbN
4
and have
one Li atom donate an electron to the Nb atom, the result is a skeleton of the type
C
C
-Li
7
VN
4
and Li
6
MoN
4
, and
Fig.
21a, b
shows their structures near the [001] projection.
There are also oxide analogues of these nitrides, Li
6
ZnO
4
and Li
6
CoO
4
, first
a
