[QE-users] Issues with SCAN functional for molecules

[Fabrizio Ferrari Ruffino]

Hello,
have you tried disabling the Fermi-hole curvature when compiling Libxc?
In some cases it is the source of convergence problems with Libxc metaGGA. You can disable it by adding the flag --disable-fhc when you configure Libxc before compiling.

Hope it helps,
Fabrizio
CNR-IOM
________________________________
From: users <users-bounces at lists.quantum-espresso.org> on behalf of Ivan Dario Arellano Ramirez <arellano at utp.edu.co>
Sent: Saturday, January 4, 2025 6:48 PM
To: users at lists.quantum-espresso.org <users at lists.quantum-espresso.org>
Subject: [QE-users] Issues with SCAN functional for molecules

Dear Quantum ESPRESSO Users,

I am currently working on the calculation of formation energies for nitrides, specifically GaN and AlN, using the SCAN functional. I am using Quantum ESPRESSO (QE) version 7.3, along with libxc version 7.0. While I have successfully calculated the energies of Ga and Al in their most stable crystalline phases, I am encountering issues with the calculation of the energy for the N2 molecule.

Despite trying various configurations—adjusting diagonalization methods, mixing mode, mixing beta, k-points, ibrav, and ecutwfc—the calculations either fail to converge after 400 iterations or terminate due to too many c-bands not converging.

I am currently using norm-conserving pseudopotentials available on the QE website, and I have also tried pseudopotentials from this repository: https://yaoyi92.github.io/scan-tm-pseudopotentials.html

Here is one of the input files I have tested:

&control
    calculation = 'scf'
    restart_mode='from_scratch',
    prefix='n2',
    tstress = .true.
    tprnfor = .true.
    pseudo_dir = '/home/pps/pbe.0.3.1/PSEUDOPOTENTIALS_NC/',
    outdir='./tmp',
    verbosity = 'high'
/
&system
  ibrav = 1,
  A = 14,
    nat= 2,
    ntyp= 1,
    ecutwfc = 100,
    ecutrho = 600,
    input_dft = 'scan'
/
&electrons
    conv_thr = 1.0d-7
    electron_maxstep = 400,
    mixing_mode = 'local-TF'
    mixing_beta = 0.1D0
    diagonalization = 'cg'
/
ATOMIC_SPECIES
N   14.007      N.pbe-nc.UPF
ATOMIC_POSITIONS (angstrom)
N    7.00000000   7.00000000   7.00000000
N    7.00000000   7.00000000   8.09760000
K_POINTS automatic
1 1 1 0 0 0

I would greatly appreciate any advice or suggestions on how to resolve these convergence issues.

Thank you,
Best regards,

Iván Arellano

Universidad Tecnológica de Pereira, Colombia.

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