[Wien] specific heat factor

[Peter Blaha]

On Wed, 23 Jun 2004, jan kunes wrote:

> There is the electronic specific heat C_v/T, which is for non-interacting
> electrons propotional to the density of states at Fermi level, printed out
> in the output of tetra. I find the convesion factor from N(E_F) in 1/Ry
> to gamma in mJ/(K^2 mol) strange:
>
> gamma=N(E_F)/2.d0*(8.617D-5)**2*(pi**2)/3.d0*2.6255D6/27.212d0*1000.d0
>
> does anybody know where the 2.6255D6 comes from? By the way conversion
> factor I normally use is gamma[mJ/K^2/mol]=0.173*N(E_F)[1/Ry] (quite
> different from wien value).

Well, Georg seems to have programmed a "secret" here.

To my understanding the conversions require k_B, Avogadros number and
E-conversions into J

2.6255D6:  This factor arises from two (or actually 3) numbers:
Avogadros number (6.022 10^23 /mol)
the energy conversion from "atomic units" to Joule, which is

27.212 * 1.60219 10^-19    (first converts hartree into eV, than eV into J)


PS: The (8.617D-5)**2 is k_B in (eV/K)^2   and this leads to this additionl
factor of 1/27.212 ....

And somewhere are hidden the factors of 2 from Ry to hartree....

Hope it fits like this. Just check it on a simple case (Cu or so), where
the gamma0 is well known.

                                      P.Blaha
--------------------------------------------------------------------------
Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
--------------------------------------------------------------------------