[QE-users] Stress in hybrid functional calculations

Thu Oct 14 15:53:35 CEST 2021

I've had the same issue a few months ago with QE6.7. I've had to switch to CP2K for this purpose, which is also open source. Note that it's build on a hybrid approach of Gaussian and plane waves basis sets. For the organic systems I simulated, 800+ Ry were required with PBE0, Coulomb truncation and long range correction, for an excellent volume and energy convergence.

Xavier
________________________________
From: users <users-bounces at lists.quantum-espresso.org> on behalf of Paolo Giannozzi <p.giannozzi at gmail.com>
Sent: Thursday, October 14, 2021 6:35 AM
To: Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org>
Subject: Re: [QE-users] Stress in hybrid functional calculations

The stress converges _very_ slowly with cutoff. The ultimate test for stress is to compare it with the numerical derivatives of the energy, computed at a _fixed_ number of plane waves. This has been done more than once and I am quite sure that the stress is correctly computed.  There are still some problems in variable-cell calculations, though, of unclear origin: https://gitlab.com/QEF/q-e/-/issues/204<https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgitlab.com%2FQEF%2Fq-e%2F-%2Fissues%2F204&data=04%7C01%7Cxavbdlt%40uic.edu%7C8efb9e51915f481c4af108d98f06e97b%7Ce202cd477a564baa99e3e3b71a7c77dd%7C0%7C0%7C637698082279068798%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=EGQceIcEn7KXch8cFnh7jGlsu2IMNzmDHUFI%2BB9lTDs%3D&reserved=0>.

Paolo

On Thu, Oct 14, 2021 at 1:17 PM Audrius Alkauskas <audrius.alkauskas at ftmc.lt<mailto:audrius.alkauskas at ftmc.lt>> wrote:
Dear all,

We have started testing the Quantum Espresso implementation of screened
Fock exchange (HSE functional), benchmarking against VASP results (the
input file below).

As a test case, we took simple bulk diamond. If we calculate the energy
as a function of the lattice constant, the resulting equilibrium lattice
parameter (3.555 A) and bulk modulus are very similar to the results
from VASP, which is nice. However, the calculated stress for the
equilibrium lattice parameter is still large (~30 kBar).  The stress is
linear as a function of the lattice constant and is ~0 for the lattice
constant 3.585 A, yielding an offset of about 0.03 A with respect to
what I assume is the "correct" HSE value. The value of 3.585 A is much
closer to the PBE result.  Are there still some issues when calculating
stresses with hybrids or we do something wrong? Energies seem OK,
stresses not (the error is not huge, but still...)

If anybody has any insights, I would be happy to get receive them.

Best,
Audrius

***
Input
***

&CONTROL
    calculation      = 'scf'
    title            = 'carbon-cubic-hse-3.556'
    verbosity        = 'high'
    nstep            = 100
    tstress          = .true.
    tprnfor          = .true.
    outdir = '/home/vytautas/HSE/C/relax/3.556'
    etot_conv_thr    = 1e-06
    forc_conv_thr    = 1e-05
    pseudo_dir       = '.'
/
&SYSTEM
    ibrav            = 1
    celldm           = 6.719866103476117
    nat              = 8
    ntyp             = 1
    nbnd             = 24
    ecutwfc          = 100
    ecutrho          = 400
    ecutfock         = 400
    input_dft        = 'hse'
    exxdiv_treatment = 'gygi-baldereschi'
    x_gamma_extrapolation = .true.
    nqx1             = 4
    nqx2             = 4
    nqx3             = 4
    celldm(1)        = 6.719866131544066
/
&ELECTRONS
    electron_maxstep = 300
    conv_thr         = 1e-08
/
&IONS
/
&CELL
/

ATOMIC_SPECIES
C 12.011 C.upf

K_POINTS automatic
4 4 4  0 0 0

ATOMIC_POSITIONS angstrom
C 0.0000000000 0.0000000000 0.0000000000
C 1.7780000000 1.7780000000 0.0000000000
C 0.8890000000 0.8890000000 0.8890000000
C 2.6670000000 2.6670000000 0.8890000000
C 0.0000000000 1.7780000000 1.7780000000
C 1.7780000000 0.0000000000 1.7780000000
C 0.8890000000 2.6670000000 2.6670000000
C 2.6670000000 0.8890000000 2.6670000000

--
Audrius Alkauskas
Center for Physical Sciences and Technology (FTMC)
Vilnius, Lithuania

email: audrius.alkauskas at ftmc.lt<mailto:audrius.alkauskas at ftmc.lt>
phone: +370 612 22281
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--
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 206, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222

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