Dear QE users,
I’m Filippo Savazzi, a PhD student from Politecnico di Torino, Italy.
I’m using QE since a couple of years, and just browsing the archives of this
mailing list or enquiring the mighty google I’ve been lucky enough that this is
actually the first time I have to post a question.
Thanks everybody for the indirect support you gave me in these years.
I’m calculating absorption energies of oxygen on a coronene molecule, as part
of a little evaluation of different available XC functionals that I’m doing.
I’m calculating the absorption energy both with respect to the molecular oxygen
and with atomic oxygen.
My problems arise when I try to calculate the energy of a single atom of oxygen
using SCAN. In this case the energy diverges until the SCF fails. I have no
troubles running the calculation on the actual system (coronene + bridged O),
neither on a molecular oxygen (triplet O2); the issue is just localised on the
single oxygen atom. My first guess was that the implementation of SCAN has
either troubles in dealing with isolated systems or with spin polarization, but
I ruled out these issues when I was able to calculate the single point energy
of an oxygen molecule. Are you aware of any other problems using SCAN in these
conditions?
In the following I attach the input for pw.x I’m using, as well as a brief
example of the SCF part in the output. I already played with cell dimension
(thinking too much vacuum could have been the problem), as well as with ecutwfc
and ecutrho (so indirectly with the integration grid), and then, just to give
it a chance, with the diagonalization method and beta-mixing.
Thank you in advance for your attention.
Best,
Filippo
Filippo Savazzi, PhD Student
Politecnico di Torino, Torino, Italy
&CONTROL
calculation = ’scf',
restart_mode='from_scratch',
pseudo_dir = '/home/filippo/pseudo',
outdir='./tmp_o',
prefix='oxy',
/
&SYSTEM
ibrav=6,
celldm(1)=20,
celldm(3)=1,
nat=1,
ntyp=1,
input_dft='scan',
ecutwfc=100,
tot_magnetization=2,
nspin=2,
/
&ELECTRONS
diagonalization = 'cg',
electron_maxstep = 300,
mixing_mode = 'local-TF',
mixing_beta = 0.7,
conv_thr = 1.0d-7,
/
&IONS
ion_dynamics='damp',
upscale=1000,
/
ATOMIC_SPECIES
O 15.99 O_ONCV_PBE-1.0.upf
ATOMIC_POSITIONS {angstrom}
O 0.0000 0.0000 0.0000
K_POINTS{gamma}
EXTRACT OF OUTPUT:
Dense grid: 540376 G-vectors FFT dimensions: ( 128, 128, 128)
Estimated max dynamical RAM per process > 116.06 MB
Estimated total dynamical RAM > 1.36 GB
Generating pointlists ...
new r_m : 0.4125 (alat units) 8.2500 (a.u.) for type 1
Initial potential from superposition of free atoms
starting charge 5.99905, renormalised to 6.00000
negative rho (up,down): 4.917E-05 4.917E-05
Starting wfcs are random
total cpu time spent up to now is 3.1 secs
Self-consistent Calculation
iteration # 1 ecut= 100.00 Ry beta= 0.70
CG style diagonalization
ethr = 1.00E-02, avg # of iterations = 9.6
negative rho (up,down): 1.044E-03 1.363E-03
total cpu time spent up to now is 240.5 secs
total energy = 2429.63502350 Ry
Harris-Foulkes estimate = -31.41616940 Ry
estimated scf accuracy < 3.28037744 Ry
total magnetization = 2.00 Bohr mag/cell
absolute magnetization = 2.00 Bohr mag/cell
iteration # 2 ecut= 100.00 Ry beta= 0.70
CG style diagonalization
c_bands: 4 eigenvalues not converged
ethr = 1.00E-02, avg # of iterations = 13.6
negative rho (up,down): 2.824E-03 3.815E-03
total cpu time spent up to now is 331.7 secs
total energy = 33638.43350785 Ry
Harris-Foulkes estimate = 318.68713998 Ry
estimated scf accuracy < 0.37936007 Ry
total magnetization = 2.00 Bohr mag/cell
absolute magnetization = 2.00 Bohr mag/cell
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