Interaction strength in BCS theory I'm looking to plot the band gap $\Delta(T)$ as a function of temperature between $T = 0$ and $T = T_c$ by numerical evaluation of the band gap equation
$$\frac{1}{\mathcal{N}(0)V} = \int_0^{\hbar\omega_D}{d\xi\frac{\tanh{\frac{\sqrt{\Delta^2+\xi^2}}{2k_BT}}}{\sqrt{\Delta^2+\xi^2}}}$$
where $\omega_D$ is the Debye frequency, $\mathcal{N}(0)$ is the density of states at the Fermi level and $V$ is the interaction strength in the BCS model. Now, in order to do this, I need values for both $\omega_D$ and $\mathcal{N}(0)V$.
I think I have a pretty good idea about the order of magnitude for $\omega_D$ if I assume longitudinal optical phonons (I find $\hbar\omega_{LO} \propto 10\,\mathrm{meV}$, but please do correct me if that doesn't seem right).
However, I still need a value for $\mathcal{N}(0)V$. Wikipedia mentions 

The energy of the pairing interaction is quite weak, of the order of $10^{−3}\,\mathrm{eV}$, and thermal energy can easily break the pairs.

but it's not clear what quantity exactly is meant by 'the energy of the pairing interaction' (I could imagine it being one of two things). I'm guessing $\mathcal{N}(0) \propto 10^{28}$ for a metal (again, correct me if I'm wrong), so my question is really quite straightforward: what is the value of the interaction strength $V$ in the BCS model? (provide a reference please)
 A: In the book by P.G. de Gennes Superconductivity of Metals and Alloys, it's written 

$N(0)V < 0.3$. 

Also written : 

Lead and mercury are two notable exceptions with low $\Theta_{D} \left( =\hslash \omega_{D}/k_{B} \right) $, giving, respectively, $N(0)V=0.39$ and $N(0)V=0.35$.

More details on p.112, P.G. de Gennes Superconductivity of Metals and Alloys, Westview (1999). The first edition dated back to 1966. To my knowledge there is no change between the editions. 
See also the table 4-1 on p.125 of the same book for several specific values for the pure metals. This table is reproduced below for commodity.
$$\begin{array}{cccc}
\mbox{Metal} & \Theta_{D}\left(\mbox{K}\right) & T_{c}\left(\mbox{K}\right) & N\left(0\right)V\\
\mbox{Zn} & 235 & 0.9 & 0.18\\
\mbox{Cd} & 164 & 0.56 & 0.18\\
\mbox{Hg} & 70 & 4.16 & 0.35\\
\mbox{Al} & 365 & 1.2 & 0.18\\
\mbox{In} & 109 & 3.4 & 0.29\\
\mbox{Tl} & 100 & 2.4 & 0.27\\
\mbox{Sn} & 195 & 3.75 & 0.25\\
\mbox{Pb} & 96 & 7.22 & 0.39
\end{array}$$
Post-scriptum:
There are (surprisingly !) nothing about this question on the book by J.R. Schrieffer, Superconductivity, Benjamin (1964). There is not even a discussion on the gap equation as far as I can check... There is a repetition of the Gennes data on the book by A.I. Fetter and J.D. Walecka, Quantum theory of many-particle systems, Dover Publications (2003, first edition 1971), p.448. But this table is less complete. 
There is also no discussion about the numerical value in the original paper by BCS [Bardeen, J., Cooper, L. N., & Schrieffer, J. R. ; Theory of Superconductivity. Physical Review, 108, 1175–1204 (1957). http://dx.doi.org/10.1103/PhysRev.108.1175 -> free to read on the APS website], but there is a possibly interesting expression (Eq.(2.40), written below in your notation / in the original BCS paper, the gap is written $\varepsilon_{0}$): 
$$\Delta\left(T=0\right)=\frac{\hslash\omega_{D}}{\sinh \frac{1}{N(0)V}}$$
which might be of help for calculating the critical line $\Delta(T)$.
