Dear Giuseppe, Thanks so much for the clarification. Now understand Jia's point and I will definitely look into trying norm conserving pseudo for my system. Thank you all for your numerous responses and help!
All the best, Martina On Thu, Apr 26, 2018 at 3:04 AM, Giuseppe Mattioli < [email protected]> wrote: > > Dear Martina > If you look at Jia’s comment from the other side, a norm conserving pseudo > might be OK with a 80/320 Ry cutoff (ONCV PPs from the sg15 library usually > are). And you get rid of all the usual limitations of US (e.g. slow or > unstable calculations with hybrid EXX functionals). > HTH > Giuseppe > > Martina Lessio <[email protected]> ha scritto: > > Dear Jia, >> >> Thanks so much for your feedback. I see your point, although that is the >> result I got from my convergence tests. Perhaps I will have another look >> at >> my tests and check that I have not been too conservative with selecting >> the >> parameters. Furthermore the suggested minimum cutoff for one of the pseudo >> potentials I am using is 50 Ry so I don't think I can go much lower than >> that. >> >> All the best, >> Martina >> >> On Wed, Apr 25, 2018 at 5:23 PM, Jia Chen <[email protected]> wrote: >> >> Dear Martina, >>> >>> If I may interject, the advantage of ultrasoft pseudopotentail is not >>> using wavefunction cutoff as large as 55 Ry. Usually ultrasoft and norm >>> conserving pseudopotential have similar density cutoff, but ultrasoft >>> only >>> need about half the wavefunction cutoff. >>> >>> Cheers >>> Jia >>> >>> On Wed, Apr 25, 2018 at 4:11 PM, Martina Lessio <[email protected]> >>> wrote: >>> >>> Dear Stefano, >>>> >>>> I have one more question regarding the convergence tests. I have >>>> performed the tests in the order that you recommended and found that if >>>> I >>>> set ecutrho=280 Ry I can get away with ecutwfc=55 Ry without negatively >>>> impacting the convergence. So I am thinking of using these parameters >>>> for >>>> my future calculations. However, I have read in many QE resources that >>>> if >>>> you use ultrasoft pseudopotentials like I do, ecutrho should be at least >>>> equal to 8*ecutwfc. So I am now wondering whether it is an issue that >>>> in my >>>> case ecutrho is only equal to about 5*ecutwfc or given that I performed >>>> the >>>> recommended convergence tests it is okay to have this setup even for >>>> pseudopotentials. >>>> >>>> I hope my question is clear. >>>> Thanks so much! >>>> >>>> All the best, >>>> Martina >>>> >>>> Martina Lessio >>>> Postdoctoral Research Scientist >>>> Department of Chemistry >>>> Columbia University >>>> >>>> >>>> On Tue, Apr 24, 2018 at 10:53 AM, Martina Lessio <[email protected]> >>>> wrote: >>>> >>>> Dear Stefano, >>>>> >>>>> Thank you very much for your prompt response, that helps a lot! >>>>> I will repeat the tests as you suggested but it's good to know that my >>>>> system is behaving normally and I can then proceed with more complex >>>>> calculations. >>>>> >>>>> All the best, >>>>> Martina >>>>> >>>>> On Tue, Apr 24, 2018 at 3:23 AM, Stefano de Gironcoli < >>>>> [email protected] >>>>> > wrote: >>>>> >>>>> Dear Martina Lessio, >>>>>> >>>>>> first of all I would say that a convergence error of 1.d-5 Ry in a >>>>>> 6 >>>>>> atom cell looks pretty much converged to me. I think that even your >>>>>> ecutrho >>>>>> = 240 Ry calculation (~1.d-5 Ry per atom) looks quite good. >>>>>> >>>>>> coming to the way things converge: >>>>>> >>>>>> - total energy convergence with respect to ecutwfc is expected to >>>>>> be >>>>>> from above because of variational principle: the higher ecutwfc is the >>>>>> more planewaves are included in the wavefunction expansion, hence the >>>>>> lower >>>>>> the energy. However in the ultrasoft pseudopotential definition the >>>>>> energy >>>>>> is not only a function of the wavefunctions but also includes a >>>>>> dependence >>>>>> on augmentation charges, that are localized and may contain higher >>>>>> Fourier >>>>>> components with respect to 4*ecutwfc ( = 240 in your case). Failing to >>>>>> include enough Fourier components in the augmentation charges will >>>>>> affect a >>>>>> number of integrals but not in a variational way... integrals would >>>>>> simply >>>>>> be inaccurate and the inaccuracy can be both from above or from below. >>>>>> >>>>>> - I would perform cutoff convergence test in a slightly different >>>>>> order: 1) I would check convergence of total energy (and stress, and >>>>>> forces) as a function of ecutwfc using the default value for >>>>>> ecutho=4*ecutwfc (that is without specifying ecutrho in the input). >>>>>> When >>>>>> this procedure converges (and it can initially converge from below >>>>>> due to >>>>>> augmentation charge Fourier components being missing) this means that >>>>>> wavefunction expansion AND augmentation-charge expansion are both >>>>>> converged. 2) I would then fix ecutrho=4*converged_ecutwfc, which >>>>>> takes >>>>>> care of augmentation charge convergence, and I would check whether I >>>>>> can >>>>>> get away with a lower ecutwfc for the wavefunction expansion. >>>>>> >>>>>> - as for k-point sampling convergence, there is no variational >>>>>> principle w.r.t. number of k-points: it's again a matter of >>>>>> convergence of >>>>>> an integral. The denser the grid the better the integral but there is >>>>>> no >>>>>> variational principle with respect to which k-point you include and >>>>>> which >>>>>> you dont. >>>>>> >>>>>> hope this helps >>>>>> >>>>>> stefano >>>>>> >>>>>> On 24/04/2018 05:56, Martina Lessio wrote: >>>>>> >>>>>> Dear Quantum Espresso community, >>>>>> >>>>>> I am new to Quantum Espresso and I am trying to run some simple >>>>>> simulations on MoTe2 bulk. Unfortunately I seem to be having some >>>>>> issues >>>>>> with some preliminary convergence tests for charge density cutoff and >>>>>> K-point grid and I am hoping to get some help from you on this. >>>>>> Here is a graph with the results of the charge density cutoff >>>>>> convergence test I performed while setting the kinetic energy cutoff >>>>>> equal >>>>>> to 60 Ry (I performed a test to set this as well): >>>>>> >>>>>> I am worried about these results because I would expect the total >>>>>> energy to go down rather than going up when I increase ecutrho. I also >>>>>> observe a similar energy trend when I increase the k-point grid, >>>>>> which also >>>>>> seems unusual and possibly wrong to me. >>>>>> I am copying below the input I have used for these calculations and I >>>>>> would greatly appreciate any help with figuring our whether I am doing >>>>>> something wrong. >>>>>> >>>>>> Thank you so much! >>>>>> >>>>>> Kind Regards, >>>>>> Martina Lessio >>>>>> >>>>>> Postdoctoral Research Scientist >>>>>> Department of Chemistry >>>>>> Columbia University >>>>>> >>>>>> &control >>>>>> >>>>>> calculation = 'scf' >>>>>> >>>>>> restart_mode='from_scratch', >>>>>> >>>>>> prefix='MoTe2_ecutwfc', >>>>>> >>>>>> pseudo_dir = '/home/mlessio/espresso-5.4.0/pseudo/', >>>>>> >>>>>> outdir='/home/mlessio/espresso-5.4.0/tempdir/' >>>>>> >>>>>> / >>>>>> >>>>>> &system >>>>>> >>>>>> ibrav= 4, A=3.530, B=3.530, C=13.882, cosAB=-0.5, cosAC=0, >>>>>> cosBC=0, >>>>>> >>>>>> nat= 6, ntyp= 2, >>>>>> >>>>>> ecutwfc =60.0 ecutrho=300. >>>>>> >>>>>> nspin =4, lspinorb =.true., noncolin=.true. >>>>>> >>>>>> / >>>>>> >>>>>> &electrons >>>>>> >>>>>> mixing_mode = 'plain' >>>>>> >>>>>> mixing_beta = 0.7 >>>>>> >>>>>> conv_thr = 1.0d-8 >>>>>> >>>>>> / >>>>>> >>>>>> ATOMIC_SPECIES >>>>>> >>>>>> Mo 95.96 Mo.rel-pbe-spn-rrkjus_psl.1.0.0.UPF >>>>>> >>>>>> Te 127.6 Te.rel-pbe-n-rrkjus_psl.1.0.0.UPF >>>>>> >>>>>> ATOMIC_POSITIONS {crystal} >>>>>> >>>>>> Te 0.333333334 0.666666643 0.625000034 >>>>>> >>>>>> Te 0.666666641 0.333333282 0.375000000 >>>>>> >>>>>> Te 0.666666641 0.333333282 0.125000000 >>>>>> >>>>>> Te 0.333333334 0.666666643 0.874999966 >>>>>> >>>>>> Mo 0.333333334 0.666666643 0.250000000 >>>>>> >>>>>> Mo 0.666666641 0.333333282 0.750000000 >>>>>> >>>>>> >>>>>> K_POINTS {automatic} >>>>>> >>>>>> 8 8 2 0 0 0 >>>>>> >>>>>> >>>>>> _______________________________________________ >>>>>> users mailing [email protected]:// >>>>>> lists.quantum-espresso.org/mailman/listinfo/users >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> _______________________________________________ >>>>>> users mailing list >>>>>> [email protected] >>>>>> https://lists.quantum-espresso.org/mailman/listinfo/users >>>>>> >>>>>> >>>>> >>>>> >>>>> -- >>>>> Martina Lessio, Ph.D. >>>>> Frontiers of Science Lecturer in Discipline >>>>> Postdoctoral Research Scientist >>>>> Department of Chemistry >>>>> Columbia University >>>>> >>>>> >>>> >>>> >>>> -- >>>> Martina Lessio, Ph.D. >>>> Frontiers of Science Lecturer in Discipline >>>> Postdoctoral Research Scientist >>>> Department of Chemistry >>>> Columbia University >>>> >>>> _______________________________________________ >>>> 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 >>> >>> >> >> >> -- >> Martina Lessio, Ph.D. >> Frontiers of Science Lecturer in Discipline >> Postdoctoral Research Scientist >> Department of Chemistry >> Columbia University >> > > > 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]> > > > _______________________________________________ > users mailing list > [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users > -- Martina Lessio, Ph.D. Frontiers of Science Lecturer in Discipline Postdoctoral Research Scientist Department of Chemistry Columbia University
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