Dear Mehmet, thanks a lot for the reply. I tried using PAW but nothing changed. So it should be something related to other aspects of my input file. Best regards, Mauro.
2014-06-09 12:22 GMT+02:00 Mehmet Topsakal <mtopsaka at umn.edu>: > I think the problem might be related with iron ultrasoft pseudopotential. > > As in page 40 of this pdf : > > http://www.vasp.at/vasp-workshop/slides/pseudopp2.pdf > > Low-spin case (NM) is okay. But for high-spin iron, energies are too > different. > > VASP use PAW potential. So you should switch to PAW with QE. > > Hope this helps. > Dear Matteo, > thanks a lot for the reply. > I tried also using occupations="smearing" but the situation is the same. I > get a difference of 0.3 electrons between the iron atom Fe1 and the other > three Fe2. > Is there anything else that I can try? Could this behaviour due to the > differences between VASP (that you used in the refererence article) and > Quantum Espresso? > Best regards, > Mauro. > > > > 2014-06-06 16:55 GMT+02:00 Matteo Cococcioni <matteo at umn.edu>: > >> >> Dear Mauro, >> >> one thing I notice is that you are using occupation fixed. is there a >> reason for that? this, I think, might actually cause the result you are not >> happy about. >> >> Matteo >> >> >> On Fri, Jun 6, 2014 at 4:39 PM, Mauro Sgroi < >> maurofrancesco.sgroi at gmail.com> wrote: >> >>> Dear all, >>> I'm trying to study the phase separation in LixFePO4 using DFT+U. >>> The reference article that I'm using is PRB 69, 201101 (R) 2004, "Phase >>> separation in LixFePO4 induced by correlation effects, Zhou et al. >>> >>> The authors compare, using VASP, standard DFT with DFT+U and obtain the >>> correct description of the material with the latter approach. In particular >>> they found that is possible to describe the formation of two type of ion, >>> Fe2+ and Fe3+, according to to the different position in the unit cell in >>> the partially lithiated structures. With GGA all Fe ions have the same >>> occupancies, regardless the position in the cell and the fact that they are >>> more or less near a lithium ion. >>> To obtain this result with DFT+U they had to force the breaking of the >>> symmetry of the structure and, I imagine, they set the initial occupations >>> in some way to force the desired electronic configuration. >>> >>> I'm trying to do the same, differentiating the Fe atoms, breaking the >>> symmetry and using starting_ns_eigenvalue to force the initial occupations. >>> My problem is that at the end of the calculation I got always the same >>> occupations on the 4 Fe atoms in the structure (more or less, the >>> difference could be 0.3 electrons). >>> >>> I'm using lda_plus_u_kind=0, but also using the other approach was not >>> beneficial. >>> >>> My input file is below. >>> Have you any suggestion? >>> >>> Thanks a lot in advance and best regards, >>> Mauro Sgroi. >>> >>> &control >>> calculation='scf', >>> pseudo_dir = "/usr2/sgroi/DATABASE/ESPRESSO", >>> prefix='lifepo4_scfU', >>> outdir='/home/dati/espresso/temp', >>> / >>> &system >>> ibrav=8, celldm(1)=19.748515, celldm(2)=0.586193, >>> celldm(3)=0.441599, nat=27, ntyp=5, nosym=.true. >>> ecutwfc=40, ecutrho=400, nbnd=130, occupations='fixed', nspin=2, >>> tot_magnetization=17, >>> lda_plus_u=.true., Hubbard_U(2)=4., Hubbard_U(3)=4.475, >>> starting_ns_eigenvalue(5,2,2)=0, >>> starting_ns_eigenvalue(4,2,2)=0, >>> starting_ns_eigenvalue(3,2,2)=0, >>> starting_ns_eigenvalue(2,2,2)=0, >>> starting_ns_eigenvalue(1,2,2)=0, >>> starting_ns_eigenvalue(5,2,3)=1, >>> starting_ns_eigenvalue(4,2,3)=0, >>> starting_ns_eigenvalue(3,2,3)=0, >>> starting_ns_eigenvalue(2,2,3)=0, >>> starting_ns_eigenvalue(1,2,3)=0 >>> / >>> &electrons >>> conv_thr=1.0d-8, electron_maxstep=100, mixing_beta=0.5 >>> / >>> >>> ATOMIC_SPECIES >>> Li 6.941 Li.pbe-s-van_ak.UPF >>> Fe1 55.847 Fe.pbe-sp-van_ak.UPF >>> Fe2 55.847 Fe.pbe-sp-van_ak.UPF >>> P 15.9994 P.pbe-van_ak.UPF >>> O 30.9737 O.pbe-van_ak.UPF >>> >>> ATOMIC_POSITIONS {crystal} >>> Fe1 0.281537138 0.250000000 0.981851206 1 0 1 >>> P 0.103893879 0.250000000 0.415586970 1 0 1 >>> O 0.119764467 0.250000000 0.744164738 1 0 1 >>> O 0.447356144 0.250000000 0.201257756 1 0 1 >>> O 0.187375840 0.060350405 0.283173864 >>> Li 0.500000000 0.000000000 0.500000000 0 0 0 >>> Fe2 0.211199573 0.750000000 0.474632077 1 0 1 >>> P 0.405092969 0.750000000 0.922566801 1 0 1 >>> O 0.401164833 0.750000000 0.251505445 1 0 1 >>> O 0.041727760 0.750000000 0.686207216 1 0 1 >>> O 0.336134397 0.956851552 0.790300073 >>> Li 0.000000000 0.500000000 0.000000000 0 0 0 >>> Fe2 0.719627852 0.750000000 0.020422522 1 0 1 >>> P 0.902369089 0.750000000 0.575773635 1 0 1 >>> O 0.896492242 0.750000000 0.246982466 1 0 1 >>> O 0.540334658 0.750000000 0.790913565 1 0 1 >>> O 0.840097513 0.539754373 0.720678002 >>> Li 0.500000000 0.500000000 0.500000000 0 0 0 >>> Fe2 0.786894270 0.250000000 0.525238732 1 0 1 >>> P 0.588956858 0.250000000 0.078832190 1 0 1 >>> O 0.587126133 0.250000000 0.749458661 1 0 1 >>> O 0.966454798 0.250000000 0.315230191 1 0 1 >>> O 0.654364669 0.453679217 0.216461848 >>> O 0.822813149 0.944845411 0.700568536 >>> O 0.653714964 0.047069624 0.216100948 >>> O 0.172021112 0.453011228 0.263457462 >>> O 0.335493673 0.543326856 0.788919121 >>> >>> K_POINTS {automatic} >>> 2 4 8 1 1 1 >>> >>> >>> _______________________________________________ >>> Pw_forum mailing list >>> Pw_forum at pwscf.org >>> http://pwscf.org/mailman/listinfo/pw_forum >>> >> >> >> _______________________________________________ >> Pw_forum mailing list >> Pw_forum at pwscf.org >> http://pwscf.org/mailman/listinfo/pw_forum >> > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum > -------------- next part -------------- An HTML attachment was scrubbed... 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