Chemistry Reference
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a
b
U
M
=6
V
MM
=3
V
MXM
=2
V
2
=2
U
M
=6
V
MM
=3
V
MXM
=3
V
2
=2
6
6
BCDW
BCDW
4
4
β
β
CDW
ACP
2
2
ACP
AV
AV
0
0
0
1
2
0
1
2
α
α
Fig. 12.7 Ground-state phase diagrams of the 12-site model for
K
MXM
¼
0, on the
a
-
b
plane for
(a)
V
MXM
¼
2 and (b)
V
MXM
¼
3. The parameters are
t
MM
¼
1,
t
MXM
¼
0.8,
K
MX
¼
6,
U
M
¼
6,
V
MM
¼
3, and
V
2
¼
2[
23
]
a
b
c
t
MXM
=0.8
K
MX
=6
t
MXM
=0.8
K
MX
=4
t
MXM
=0.5
K
MX
=6
CDW
CDW
CDW
6
6
6
CP
CP
ACP
β
β
β
CP
4
4
4
ACP
ACP
AV
AV
AV
2
2
2
0
0.4
0.8
0
0.4
0.8
0
0.4
0.8
α
α
α
Fig. 12.8 Ground-state phase diagrams of the 8-site model for
K
MXM
¼
1, on the
a
-
b
plane, for
(a)
t
MXM
¼
0.8,
K
MX
¼
6, (b)
t
MXM
¼
0.8,
K
MX
¼
4, and (c)
t
MXM
¼
0.5,
K
MX
¼
6. The
parameters are
t
MM
¼
1,
U
M
¼
6,
V
MM
¼
1.5,
V
MXM
¼
1, and
V
2
¼
0.5 [
23
]
states are replaced by the CDW states for the smaller
K
MX
. If we want to explain the
difference between the pop and dta systems simply by the difference in
K
MX
(not in
K
MXM
as we do in this paper), we need larger
K
MX
for the dta systems, contrary to
the intuition. In Fig.
12.8c
, we change only
t
MXM
from the parameters of Fig.
12.8a
:
t
MXM
¼
0.5. The ACP phase is the most affected by this change and destabilized by
the reduction of
t
MXM
. This is because the energy gain from forming a singlet pair
of electrons (on the nearest-neighbor M sites accompanied with an X site in-
between) is proportional to
t
MXM
2
. Meanwhile, the boundaries between the AV
and CP phases and those between the CP and CDW phases are not much affected by
the change of
t
MXM
. It is not regarded as a main mechanism for the variation of the
electronic phases in R
4
[Pt
2
(pop)
4
I]
n
H
2
O.
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