Chemistry Reference
In-Depth Information
Table 2 Underlying nets in carbonates
Underlying
net
Correspondence
a
Carbonate
CO
3
coordination
type
T
6
;T
33
;T
51
pcu-b
(NaCl)
MCO
3
(M
¼
Mg, Ca, Sr, Ba, Mn, Fe, Co,
Ni, Zn, Cd)
Normal
T
33
T
6
MCO
3
(M
¼
Ca, Sr, Ba, Pb, Eu)
nia (NiAs)
Anti
Normal
(vaterite)
T
44
bcu (CsCl)
CaCO
3
-HP
Normal
T
32
sqp (SnP)
CuCO
3
Normal
T
8
flu (CaF
2
) i
2
CO
3
Anti
T
(12)
alb (AlB
2
) i
2
CO
3
-HP
Anti
T
74
;T
83
Ni
2
In (BaF
2
-
HP)
M
2
CO
3
(M
¼
Na, K, Rb, Cs)
Anti
T
(10)
fit (MoSi
2
)
2
CO
3
-LT
Anti
a
Hereafter two kinds of correspondences of M cations and XO
n
anions to the atoms of a binary
compound A
y
X
z
(if any) are given in tables:
normal
or
anti
if the M cations match the electroposi-
tive atoms A or electronegative atoms X, respectively
Fig. 3 The NaCl net (
Fm
3
m
) and some related nets of oxoacid salts: CaCO
3
(calcite) and
isostructural MBO
3
, MNO
3
(
R
3
c
); BaSeO
3
and isostructural PbSO
3
, MSeO
3
, KClO
3
(
P
2
1
/
m
);
BaSO
4
-HT and isostructural MSO
4
, MClO
4
(
F
43
m
). Hereafter by default an M atom is placed in
the center of the net fragment for any oxoacid salt. Only one representative of each isostructural
series is shown
1:1. This group of carbonates contains the most abundant CaCO
3
minerals
(calcite and aragonite) as well as the related magnesite (MgCO
3
), strontianite
(SrCO
3
), witherite (BaCO
3
), and cerussite (PbCO
3
). The calcite and aragonite
structure types can be described as oxygen-stuffed NaCl (pcu-b) and
anti
-NiAs
(nia), respectively; M
2+
and CO
3
2-
ions in the aragonite type correspond to As and
of M
2+
cation and the topological motif: large cations stabilize the aragonite type.
g
¼
