Chemistry Reference
In-Depth Information
µ
-(TMTSF)
2
ClO
4
.
Figure 6.32. (a) Band structure and FS of
=
(0
,
0), X
=
(
a
∗
/
b
∗
/
(
a
∗
/
b
∗
/
a
∗
/
b
∗
/
2) with
a
=
1
2
,
0), Y
=
(0
,
2), M
=
2
,
2), S
=
(
−
2
,
2
(
b
+
a
) and
b
=
b
. (b) Band structure and FS of triclinic (TMTSF)
2
ClO
4
. Reprinted
with permission from Perruchas
et al.
, 2005.
identical to those in (TMTSF)
2
ClO
4
, the overlap between all TMTSF molecules
being the same. The electronic structure of
µ
-(TMTSF)
2
ClO
4
is reported in
Fig. 6.32(a).
The cell axes are chosen so that
a
is the interstack direction as for
µ
-
(TMTSF)
2
ReO
4
. For comparison, the band structure and the FS of (TMTSF)
2
ClO
4
have been calculated using the same cell axes and are also reported in Fig. 6.32(b).
Both are very similar but the band dispersions in
µ
-(TMTSF)
2
ClO
4
are approx-
imately 20% weaker than in (TMTSF)
2
ClO
4
. Then interactions between TMTSF
molecules in the organic slabs are slightly weaker in the new phase favouring
electronic localization. Moreover, the FSs calculated for the two salts, although
similar, exhibit slightly different nesting vectors, which means that the interstack
interactions are also somewhat different in the two polymorphs. Thus, despite the
structural similarity, the physical behaviour of the two polymorphs could well be
different. Clearly, conductivity measurements are needed, but for the time being
µ
-(TMTSF)
2
ClO
4
is a disappearing polymorph (Dunitz & Bernstein, 1995). See
page 49 for the definition of a disappearing polymorph.
