Chemistry Reference
In-Depth Information
(a)
(b)
(c)
Figure 1.9. (a) View of the 218 K crystal structure of C
6
H
6
along the
b
-direction,
Pbca
,
a
692 nm. Crystal structure from Bacon
et al
., 1964. (b)
ab
-plane of coronene.
P
2
1
/
=
0
.
744 nm,
b
=
0
.
955 nm,
c
=
0
.
a
,
a
=
1
.
610 nm,
b
=
0
.
469 nm,
8
◦
. Crystal structure from Robertson & White, 1945.
(c)
bc
-plane of heptafulvalene.
P
2
1
/
c
=
1
.
015 nm,
β
=
110
.
c
,
a
=
0
.
969 nm,
b
=
0
.
773 nm,
c
=
0
.
697
03
◦
. Crystal structure from Thomas & Coppens, 1972.
nm,
β
=
98
.
1.5 Molecular organic materials
When classifying a given material according to its physical properties, the common
tendency is to emphasize the most important property: metallicity, superconduc-
tivity, magnetic order, etc. However, strictly speaking one has to specify which
point in the phase diagram is being considered, hence indicating the corresponding
external variables
P
,
T
,
B
, etc., since the same material can behave differently
when spanning the parameter hyperspace. The parameter hyperspace consists of
the set of variables and will be defined in detail in Chapter 3. For instance, a given
material can be a metal above a given temperature but a semiconductor below
