[QE-users] Question on the handling of the analytical

[Lorenzo Paulatto]

Dear Erik,

you question is extremely vast and would require hours to answer in detail.

The starting point for the theory used in QE is the "code" paper 
doi:10.1088/0953-8984 and reference 46 therein: NIelsen & Martin 
10.1103/PhysRevB.32.3780. There are more, quite complicated therms 
related to ultrasoft pseudoptentials.

- Are the dependencies of the cell vectors on the reciprocal lattice 
vectors G taken into account during a vc-relaxation?


no, but relax is done at constant number of plane waves (not constant 
cutoff)


- If so, how is the coupling between these terms treated?


I'm not sure what you mean, but I think there is not


- Are the analytical gradients completely expressed in cartesian 
coordinates?


Is there are many terms (hartree, XC, local, gradient correction...) it 
is very possible that some terms are computed in cartesian coordinates, 
others on the basis of lattice vectors. From a quick look at the code, I 
think they are mostly done directly in cartesian coordinates.

hth


On 11/11/25 17:12, Erik Hansen via users wrote:
>
> Dear Quantum ESPRESSO users and developers,
>
> I am writing to follow up on my previous inquiry.
>
> As I am currently working at the code level with Quantum ESPRESSO, I 
> am particularly interested in understanding how the analytical 
> gradients are handled internally during a variable-cell (vc-) 
> relaxation. Specifically:
>
> - Are the dependencies of the cell vectors on the reciprocal lattice 
> vectors G taken into account during a vc-relaxation?
>
> - If so, how is the coupling between these terms treated?
>
> - Are the analytical gradients completely expressed in cartesian 
> coordinates?
>
> Thank you very much for your time and assistance,
>
> Best regards
>
> Erik Hansen
>
> ——————————————————————————**
>
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-- 
Dr. Lorenzo Paulatto
IR IMPMC - CNRS UMR 7590 / Sorbonne Université / MNHN
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