Finding the Error in Computing Spherical Tensor of Rank 0 Using General Formula

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SUMMARY

The discussion focuses on the computation of the spherical tensor of rank 0, specifically ##T_0^{(0)}##, using the general formula from Sakurai (3.11.27). The initial computation incorrectly used the Clebsch-Gordan coefficients, leading to an erroneous result. The correct Clebsch-Gordan coefficient for the term ##\langle 1,1;1,-1|1,1;0,0\rangle## is ##\frac{1}{\sqrt{3}}##, which adjusts the final expression for ##T_0^{(0)}## to ##\frac{1}{\sqrt{3}}(U_{1}^{(1)} V_{-1}^{(1)} + U_{0}^{(1)} V_{0}^{(1)} + U_{-1}^{(1)} V_{1}^{(1)})##.

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TL;DR
Coeffcient of spherical tensor of rank 0 from Clebsch_Gordan
This should be a trivial question. I am trying to compute the spherical tensor ##T_0^{(0)} = \frac{(U_1 V_{-1} + U_{-1} V_1 - U_0 V_0)}{3}## using the general formula (Sakurai 3.11.27), but what I get is:
$$
T_0^{(0)} = \sum_{q_1=-1}^1 \sum_{q_2=-1}^1 \langle 1,1;q_1,q_2|1,1;0,q\rangle U_{q_1}^{(1)} V_{q_2}^{(1)} \;\;\;\; \text{for} \; q = q_1 + q_2
$$
$$
T_0^{(0)} = \langle 1,1;1,-1|1,1;0,0\rangle U_{1}^{(1)} V_{-1}^{(1)} + \langle 1,1;0,0|1,1;0,0\rangle U_{0}^{(1)} V_{0}^{(1)} + \langle 1,1;-1,1|1,1;0,0\rangle U_{-1}^{(1)} V_{1}^{(1)}
$$
But this is ##T_0^{(0)} = \frac{(U_1 V_{-1} + U_{-1} V_1 - U_0 V_0)}{\sqrt{3}}##, if I read the Clebsch-Gordan coefficients correctly. Where did I make a mistake?
 
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You made a mistake in the Clebsch-Gordan coefficient. The correct coefficient is $\langle 1,1;1,-1|1,1;0,0\rangle = \frac{1}{\sqrt{3}}$, not $1$. Therefore, you should have $$T_0^{(0)} = \frac{1}{\sqrt{3}}(U_{1}^{(1)} V_{-1}^{(1)} + U_{0}^{(1)} V_{0}^{(1)} + U_{-1}^{(1)} V_{1}^{(1)})$$
 

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