Chemistry Reference
In-Depth Information
x
θ
B
θ
A
R
z
ϕ
y
A
B
x
.
θ
z
A
B
y
Figure 11.5 Top, the three angles specifying the relative orientation of two linear
molecules. Bottom: the system atom A-linear molecule B
form can be written as
<
:
j
i
j
j
j
i
4
X
i
X
j
a
4
X
i
X
j
a
j
j
j
«
«
«
«
1
1
j
i
a
j
i
a
j
A
¼
;
B
¼
j
i
þ«
j
j
j
i
þ«
j
«
«
ð
11
:
42
Þ
j
j
«
i
þ«
4
X
i
X
j
a
i
4
X
i
X
j
a
j
j
«
«
«
i
«
j
«
i
þ«
j
1
1
i
i
j
C
¼
a
;
D
¼
a
j
j
For two identical linear molecules, there are three independent disper-
sion constants, since C
¼
B.
Spherical tensor expansion of the product r
1
12
r
1
1
0
2
0
(Wormer, 1975;
Magnasco and Ottonelli, 1999a) allows us to write the leading (dipole-
dipole) term of the long-range dispersion interaction between two linear
molecules in the form:
disp
2
E
¼
R
6
C
6
ðu
A
; u
B
; wÞ
ð
11
:
43
Þ
