[QE-users] Why do I get a warning when using PWTK with HSE?

[Tone Kokalj]

Dear Salma,

The reason that both vc-relax and PWTK fail to get a lattice parameter
for HSE is related to a problem with stress calculation for hybrid
functionals. For your input, the pressure is positive even for
considerably overestimated lattice parameters (I used QE 7.1). There is
apparently an issue about stress for hybrid functionals, see:
https://gitlab.com/QEF/q-e/-/issues/204

To calculated the lattice parameter with PWTK, you can instruct it to
avoid using stress. This can be achieved as follows:

EOS {
    mode = range
    npoints = 11
    amin = 11.0
    amax = 12.0
    use_stress = .false.
}
eos_run CuI

Best regards,
Tone
-- 
Jožef Stefan Institute, Ljubljana, Slovenia


On Tue, 2023-07-11 at 09:26 +0000, NAIMI SALMA wrote:
> Hello everyone,
> 
> As I couldn't get the optimized lattice parameter for my material by
> vc-relax calculation, I used pwtk to get the optimized lattice
> parameter of my material with HSE.
> 
> In the input I used the experimental lattice parameter. But for the
> last calculated 2 points I get a warning in the terminal that the
> used a0 is too small even though that I used the experimantal one.
> That's the message that I receive :
> 
> ```
> ---------------------------------------------------------------------
> ---
> WARNING: from get2pV0_: two-point Murnaghan estimation of lattice-
> parameter failed.
>                   The initial a0 was too small.
> ---------------------------------------------------------------------
> ---
> 
>       poor-man estimate of unit-cell volume :  V0 =  3536.06 bohr^3
>       poor-man estimate of lattice-parameter:  a0 =    15.23 bohr
> 
> 
>       warning: minimum is not bracketed yet, calculating another
>                estimator point.
> 
>       * calculating estimator point #.5 :  a =  15.997 bohr
> 
>       Executable: /home/salma/Desktop/qe-7.0/bin/pw.x
>       Running: pw.x -in my_input.d/my_input.estimator-5.in >
> my_input.d/my_input.estimator-5.out
> 
> 
>       * E(tot) = -566.98612068 ryd
>       * P      = 7.34 kbar
> 
> 
>       warning: minimum is not bracketed yet, calculating another
>                estimator point.
> ABORT: cannot guess correct a0 in 5 steps. Initial a0 must be too far
> off, retry with better a0 estimation.
> ABORT statement executed in: run_auto_ my_input.d/my_input
> ```
> 
> How can I solve this problem, please?
> 
> 
> PS: I didn't face the same issue when working with PWTK and GGA, I
> got a lattice parameter close to the experimental one in the output.
> 
> 
> 
> 
> 
> 
> 
> ------------------------------------------------------------ 
> Salma NAIMI
> PhD student - Mohamed 5 University-Rabat
> 
> 
> 
> 
> 
> 
> 
> 
> _______________________________________________
> The Quantum ESPRESSO community stands by the Ukrainian
> people and expresses its concerns about the devastating
> effects that the Russian military offensive has on their
> country and on the free and peaceful scientific, cultural,
> and economic cooperation amongst peoples
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
> users mailing list users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users