Chemistry Reference
In-Depth Information
Crystal Structures of Inorganic Oxoacid Salts
Perceived as Cation Arrays: A Periodic-Graph
Approach
Vladislav A. Blatov
Abstract A total of 569 crystal structures of anhydrous simple salts M
y
(LO
3
)
z
(L
Si, Ge, P, As, S, Se, Cl, Br, I)
are considered as three-periodic nets of M
y
(L/X)
z
, where M are cations derived
from metal atoms whereas (L/X) are conventional cations derived from nonmetal
atoms. Both L and X cations are located in the centers of triangular/trigonal-
pyramidal LO
3
and tetrahedral XO
4
oxoanions, respectively. The cation arrays
(M
¼
B, C, N, S, Se, Te, Cl, Br, I) and M
y
(XO
4
)
z
(X
¼
L/X) are proved to be the elements determining and governing the topology
of the respective crystal structures, whereas the oxygens seem to play a secondary
role as links between the cations. The preponderant role of cations in determining
the crystal structures is founded on a greater uniformity (regularity) of their arrays
when compared with those of anions or, even, with mixed cation-anion arrange-
ments. In about three-fourth of the crystal structures analyzed in this work, the
cation arrays appear to be topologically equivalent to some binary compounds, such
as NaCl, NiAs, FeB, and
þ
-Al
2
O
3
. The influence of both charge and size on the
resulting array topology is also studied in detail. A quasi-binary representation
M
y
[L/X]
z
is proposed as a general model for the crystal structures of these anhy-
drous oxoacid salts.
a
Keywords Cation arrays, Ionic packings, Oxoacid salts, Periodic graph, Software
and databases
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2 Periodic-Graph Approach in Crystal Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.2 The Concepts of Structure Representation, Underlying Net, and Packing Net . . . . . . 37
2.3 Computer Tools to Study Periodic Graphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
