# Tc for superconducting system

Hello everyone, Do you know any equation can help me to calculate the Coulomb pseudo-potential mu*, cause I'm working on McMillan formula
Tc= thetaD/1.45 {-1.04(1+lamda)/[ lamda – mu*(1+ 0.62 lamda)]}

trying to find the critical temperature Tc for a superconducting system I only have three given quantities:
Lamda= 1.04 (the electron-phonon coupling constant)
N(Ef)= 18.26 state/atom.eV (density of states DOS)
I'm not still sure of this If it's correct or not cause I found many other formulas with different details. offcourse I get this formula from the net, I first choose mu*= 0.1 as most solutions but the prophesier said it's wrong to choose it arbitrarily I have to calculate mu* using the density of state. so I searched the net to find an equation that relates mu* to DOS I found one, but it was very complicated with another unknown quantities like the volume (volume of what, how can I find it from the given numbers and as far as I know the volume of the lattice- assume- couldn't be calculated from them ) It's like self learning of something completly new and never taught before -mybe that's why I couldn't find a way to figure that out. I tried for a week before typing this. I really need to do this please help If any one can, I appreciate all the help I'll have.

Desperate physicist You might want to check out "Principles of Electron Tunneling Spectroscopy " by E L Wolf

ZapperZ
Staff Emeritus
I'm sorry it took a while to respond to this. Most of my text (and my journal access) are either at work, or from work, so most of the stuff I needed to refer to to answer this weren't available to me till today (since I am now at work).

The reference to Wolf's tunneling text isn't as useful because he simply stated it (pg. 523) and then gave you a reference to McMillan's paper (unless I missed it elsewhere in the text).

What you need is the original McMillan's paper (Phy. Rev. 167, 331 (1968)). Look at Eq. 13 of that paper, which was derived in another paper by Morel and Anderson (reference given therein). This is where you need to use the info that you have on the DOS.

Zz.

I'll see thanks.