Chemistry Reference
In-Depth Information
Fig. 1 Coordination sequence (CS), extended point symbol (ES), point symbol (PS), and vertex
symbol (VS) for the uninodal 2-periodic net fes. A 10-circuit is selected that is not a ring (it has a
shortcut and composed of two smaller 4- and 8-rings). The nodes of the first five coordination
shells are marked by the ordinal number of shell; the initial atom of the sequence formally
corresponds to the zero coordination shell
Table 1 Topological indices in pcu-b, nia, and related 6-coordinated nets
Net (representative)
Net point symbol
Coordination sequence N
1-5
{4
12
.6
3
}
pcu-b (NaCl)
Na, Cl: 6 18 38 66 102
{4
12
.6
3
}{4
9
.6
6
}
nia (NiAs)
Ni: 6 20 42 74 114
As: 6 18 42 74 114
{4
10
.6
5
}
sev-6-
C
2/
m
(
b
-HgSeO
3
)
Hg, Se: 6 19 42 74 115
{4
10
.6
5
}{4
11
.6
4
}
HIYXUJ (CaSeO
3
)
Ca: 6 18 40 70 108
Se: 6 19 40 70 108
{4
8
.6
6
.8}{4
13
.6
2
}
FEQWOO (NaIO
3
)
Na: 6 16 42 72 114
I: 6 20 42 74 114
For example, in the NaCl structure (topological type pcu-b) there are two chemi-
cally and crystallographically different atoms, but both Na and Cl are topologically
identical since they possess the same set of topological indices (the net point
symbol coincides with the point symbols of Na and Cl; Table
1
).
On the contrary, in NiAs (topological type nia) Ni and As atoms are topologi-
cally different, in spite of having similar indices, also close to those of NaCl. In
particular, the point symbols of Ni and Na(Cl) are the same {4
12
.6
3
}, i.e., in both
cases the minimal circuits of bonds are the same (12 fourfold and 3 sixfold circuits).
Other nets collected in Table
1
can also be considered as similar to either pcu-b or
nia, as it will be discussed below.
