the third derivatives that are computed in D3 are those of type
d3E/du(q) du(-q) du(0) where at least one q-vector is 0.
For the generalization to any set of displacements you need to wait for
Lorenzo's contribution.
stefano
On 20/04/2016 14:51, Sabry Gad Al Hak Moustafa wrote:
Thanks Stefano;
But, what do you mean by "some"? I am interested specifically in Fe at
high pressure, so, can QE do 3rd derivative for that?
Here
http://www.quantum-espresso.org/wp-content/uploads/Doc/ph_user_guide.pdf
it says
"D3/d3.x: calculates anharmonic phonon lifetimes (third-order
derivatives of the energy), using data produced by pw.x and ph.x (USPP
and PAW not supported)."
So, it looks like it is NCPP.
Thanks;
Sabry
==================================================
Sabry G. Moustafa, Ph.D.
Department of Chemical and Biological Engineering
511 Furnas Hall
University at Buffalo, The State University of New York
Buffalo, NY 14260-4200
716-645-1186 (office)
716-239-8543 (cell)
E-mail: [email protected] <mailto:[email protected]>
On Wed, Apr 20, 2016 at 12:28 AM, stefano de gironcoli
<[email protected] <mailto:[email protected]>> wrote:
the phonon code evaluates second order derivatives (dynamical
matrices).
this is available for NCPP, USPP and PAW
the D3 code computes some of the third order derivatives.
it is working for NCPP only as far as I remember.
forth order derivatives are not computed.
stefano
On 20/04/2016 06:34, Sabry Gad Al Hak Moustafa wrote:
Hi;
Was wondering if QE can compute 2nd, 3rd and 4th energy
derivatives in the DFPT framework? If so, is available in PAW, or
just PPs?
Thanks;
Sabry
==================================================
Sabry G. Moustafa, Ph.D.
Department of Chemical and Biological Engineering
511 Furnas Hall
University at Buffalo, The State University of New York
Buffalo, NY 14260-4200
716-645-1186 (office)
716-239-8543 (cell)
E-mail: [email protected] <mailto:[email protected]>
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