[Pw_forum] lambda calculation from the a2F(w) files

[Malgorzata Wierzbowska]

On Wed, 31 Jan 2007, Alexander Hernandez wrote:

>
> Dear pw_users,
>        does someone know which is the normalization of the a2F function
> generated by the espresso 3.2 during an electron-phonon calculation?
>
> We tried to reproduce the lambda values generated by matdyn.f90 using
> the a2F(w) files. At first, we used the formula that appears in the
> majority of the papers, including the McMillan and the Allen-Dynes
> papers that is  (lambda=2*\int a2F/w dw), and we could not obtain the
> same results. A quick inspection of the source code suggests that in
> order to used the above formula, the a2F values should first be divided
> by  2*pi. Or what is the same, one should instead use the formula
> (lambda=(1/\pi)*\int a2F/w dw) that seems to be implemented in matdyn.
> Is this correct?
>

    Dear Alexander,
    You need to divide it by 2*pi*DOS(both spins) before
    using it in McMillan's formula.
    I attach here the latex files with the equations --
    because the postscript was too big for the forum.
    The most relevant for your question are Eqs. 2, 3, 5 and 6.

    Gosia
PS. I hope you know how to generate ps-file and the latex
     source is not too big.
PSS. Now I have a question: how to make some files public
      from my account?


> Thanks in advance,
> Alexander
>
>
>
>
>
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