Dear all,
I have a question about zero point energy calculation. According to a article
called "Tutorial on calculating phonons: comparing the linear response and the
small displacement methods", author states that we can calculate zero point
energy use the results obtained with linear response method, i.e phonon code in
pwscf. Calculated steps as follows(for example Al):
(1) > pw.x < Al.scf (This generates the self-consistent wave-function)
(2) > ph.x < Al.ph.in (This generate the dynamic matrices)
(3) > q2r.x < q2r.in (Obtaining force constant matrix)
(4) > matdyn.x < matdyn.in (Calculating the phonon dispersions)
(5) > matdyn.x < phdos.in (Calculating phonon density of states)
and this will produce a file called "Al.phdos" which contains the phonon
density of states. Now by typing:
awk '{e=e+2*1/2}END{print e/33.357*4.1357/1000}' Al.phdos
and you should see that the zero point energy. The question is, I do not
understand the meaning of "{e=e+2*1/2}END{print e/33.357*4.1357/1000}", is this
appropriate for the calculation of zero point energy?
In addition, In mail list, by calculating phonons all over the Brillouin
zone (in practice, on a regular grid), and zero point energy by calculating
{\hbar\over 2} \sum_{{\bf q},\nu} \omega_{{\bf q},\nu}. I do not understand the
meaning of {\hbar\over 2} \sum_{{\bf q},\nu} \omega_{{\bf q},\nu} well. Anyone
who help me will be appreciated.
Many thanks
Best regards
Lihui
--
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Lihui Ou
PH.D Candidate in Electrochemistry
College of Chemistry and Molecular Science
Wuhan University,430072,Hubei Province,China
E-mail:oulihui666 at 126.com
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