Thank you very much Natalie, Paolo and Giuseppe You’ve been very helpful, cause I had the suspect SCAN wasn’t applicable to this subject but I was stuck trying to find tricks to make it work. I’d have just a last question on the topic. I was able to calculate the single point energy of molecular oxygen (O2) using SCAN, hence calculate the absorption energy for a bridged oxygen on coronene at least with respect to O2. Shall I consider this result satisfactory, having used the same grid that I used for other functionals (PBE, PBE0, …)? The absorption energy is consistent with the others.
Thank you again for your help, have a great day! Filippo Filippo Savazzi, PhD Student Politecnico di Torino, Torino, Italy > On 21 Nov 2018, at 21:26, Paolo Giannozzi <[email protected]> wrote: > > I tend to agree with Natalie's conclusions. Unfortunately I am not aware of > any simple solution. All meta-GGA functionals do strange things in systems > with regions of vanishing charge, and SCAN is the one that gives less > problems (!). SCF divergence is maybe extreme, but there are also problems > like this one: https://gitlab.com/QEF/q-e/issues/32 > <https://gitlab.com/QEF/q-e/issues/32>, indicating that one may need a > surprisingly dense FFT grid to get reliable results > > Paolo > > On Wed, Nov 21, 2018 at 8:22 PM Holzwarth, Natalie <[email protected] > <mailto:[email protected]>> wrote: > I have looked into the SCAN functional for an isolated atom, also finding > that Vxc increases to unphysically large values as the density decreases > exponentially. We were able to demonstrate for ourselves that the SCAN > functional itself is responsible for this behavior due to the appearance of > the density in denominators of various terms. It is my understanding that > the SCAN developers are aware of this issue and are working on a remedy. > In the meantime, perhaps it would be good to use the SCAN functional only for > systems that do not have exponentially decreasing densities. At least that > was my conclusion. Sincerely, Natalie Holzwarth > > N. A. W. Holzwarth email: > [email protected] <mailto:[email protected]> > Department of Physics web: > http://www.wfu.edu/~natalie <http://www.wfu.edu/~natalie> > Wake Forest University phone: 1-336-758-5510 > Winston-Salem, NC 27109 USA office: Rm. 300 Olin Physical > Lab > > > On Wed, Nov 21, 2018 at 1:26 PM Filippo Savazzi <[email protected] > <mailto:[email protected]>> wrote: > Thanks Giuseppe, > I’ll give it a try, I didn’t think about setting the occupation from input. > Thank you for your help. > > Best, > > Filippo > > > > Filippo Savazzi, PhD Student > Politecnico di Torino, Torino, Italy > > > On 21 Nov 2018, at 19:00, Giuseppe Mattioli <[email protected] > > <mailto:[email protected]>> wrote: > > > > > > Dear Filippo > > Isolated open-shell atoms are tricky. Please look here for hints > > > > yourpathtoQE6.3/PW/examples/example05 > > > > HTH > > Giuseppe > > > > Quoting Filippo Savazzi <[email protected] > > <mailto:[email protected]>>: > > > >> 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 > > > > > > > > GIUSEPPE MATTIOLI > > CNR - ISTITUTO DI STRUTTURA DELLA MATERIA > > Via Salaria Km 29,300 - C.P. 10 > > I-00015 - Monterotondo Scalo (RM) > > Mob (*preferred*) +39 373 7305625 > > Tel + 39 06 90672342 - Fax +39 06 90672316 > > E-mail: <[email protected] <mailto:[email protected]>> > > > > _______________________________________________ > > users mailing list > > [email protected] <mailto:[email protected]> > > https://lists.quantum-espresso.org/mailman/listinfo/users > > <https://lists.quantum-espresso.org/mailman/listinfo/users> > > _______________________________________________ > users mailing list > [email protected] <mailto:[email protected]> > https://lists.quantum-espresso.org/mailman/listinfo/users > <https://lists.quantum-espresso.org/mailman/listinfo/users>_______________________________________________ > users mailing list > [email protected] <mailto:[email protected]> > https://lists.quantum-espresso.org/mailman/listinfo/users > <https://lists.quantum-espresso.org/mailman/listinfo/users> > > -- > Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche, > Univ. Udine, via delle Scienze 208, 33100 Udine, Italy > Phone +39-0432-558216, fax +39-0432-558222 > > _______________________________________________ > users mailing list > [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users
_______________________________________________ users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
