[Pw_forum] Debye temp, phonon DOS and sum rules.

[Paolo Giannozzi]

On Jan 25, 2007, at 17:59 , Miguel Martínez Canales wrote:

> On a side note, the difference between a 40 40 40 and a 12 12 12  
> phonon
> dos is like night and day. Is such difference to be expected?

maybe not like "day and night", but it takes quite a dense grid
if you want to see a DOS with all the singularities as in textbooks

> I suppose it's related to the way the phonon dos is computed within  
> the code.

it is a rather straightforward tetrahedron method

> Finally, it might interest you to know that fitting a parabola to  
> the low w
> regime and using the pseudopotential's equilibrium lattice parametre,
> the Debye temperature is 152 K, very close to the value presented in
> Table 23.3 of Ashcroft's and Mermin's book.

so now we know that Ashcroft's and Mermin's book is correct :-)

Paolo
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Paolo Giannozzi, Democritos and University of Udine, Italy