[QE-users] DFT+U can not converge

Giuseppe Mattioli giuseppe.mattioli at ism.cnr.it
Wed Dec 19 12:30:51 CET 2018


Dear Liang Xiongyi

In my opinion, your initial structure is possibly wrong or missing  
necessary saturation (i.e. twofold-coordinated P atoms on the surface  
and P=O free terminations, which are likely unstable in gas phase).  
However, and generally speaking, if your calculation is going  
somewhere not so far from convergence, you can overcome a difficult  
initial step by using this very useful switch:

     scf_must_converge=.false.

Coupled with a suitable electron_maxstep variable, it will calculate  
forces and move atoms when scf ends. If the structure is meaningful  
and not wrong (and this may not be the case) in a few steps you should  
recover an acceptably smooth convergence.
HTH
Giuseppe

LEUNG Clarence <liangxy123 at hotmail.com> ha scritto:

> Dear QEusers,
>
> When I use QE6.3 to perform DFT+U to relax a slab, it is very  
> difficult to converge and even can not converge (more than 300 scf  
> steps). Thanks for your suggestion in advances.
>
> The input file is:
>
> &CONTROL
>   calculation='relax',
>   nstep = 200 ,
>   wf_collect = .true. ,
>   etot_conv_thr = 3.5D-6 ,
>   forc_conv_thr = 4.0D-4,
> /
>
> &SYSTEM
>   ibrav=0,
>   celldm(1)=9.6431795847d0,
>   nat=109,
>   ntyp=3,
>   ecutwfc=60,
>   ecutrho=480,
>   input_dft='PBE',
>   occupations='smearing',
>   smearing = 'gaussian' ,
>   degauss = 0.01 ,
>   nspin = 2 ,
>   starting_magnetization(1) = 0.5 ,
>   lda_plus_u = .true. ,
>   Hubbard_U(1) = 3.32 ,
>   vdw_corr = dft-d3 ,
> /
> &ELECTRONS
>   conv_thr=1d-05,
>   mixing_beta=0.3d0,
>   mixing_mode ='local-TF',
>   electron_maxstep = 600 ,
> /
> &IONS
> /
> &CELL
> /
>
> ATOMIC_SPECIES
>   Co 58.933200d0 Co.pbe-spn-rrkjus_psl.0.3.1.UPF
>   O 15.999400d0 O.pbe-n-rrkjus_psl.1.0.0.UPF
>   P 30.973800d0 P.pbe-n-rrkjus_psl.1.0.0.UPF
>
> ATOMIC_POSITIONS {crystal}
> O        0.175510868   0.823201091   0.004041902    0   0   0
> Co       0.752963028   0.655948399   0.004313566    0   0   0
> O        0.301125723   0.416151961   0.004879997    0   0   0
> Co       0.846799898   0.775755648   0.005275182    0   0   0
> Co       0.346800351   0.275755641   0.005275204    0   0   0
> O        0.392474471   0.135359341   0.005670234    0   0   0
> Co       0.940637166   0.895562903   0.006236666    0   0   0
> O        0.518089326   0.728310212   0.006508330    0   0   0
> O        0.902313840   0.059368885   0.017959393    0   0   0
> O        0.807187857   0.964594997   0.020457557    0   0   0
> O        0.036878250   0.705581722   0.023890599    0   0   0
> P        0.893919682   0.538810250   0.026242849    0   0   0
> Co       0.451343782   0.481124665   0.033750041    0   0   0
> O        0.028914218   0.314809876   0.034323347    0   0   0
> P        0.323165643   0.700374526   0.044655886    0   0   0
> O        0.412931350   0.644218586   0.045243797    0   0   0
> O        0.180081232   0.532598515   0.046685149    0   0   0
> O        0.551818853   0.324973894   0.062282695    0   0   0
> O        0.318968869   0.213353805   0.063724007    0   0   0
> P        0.408734429   0.157197863   0.064311920    0   0   0
> O        0.702985853   0.542762514   0.074644459    0   0   0
> Co       0.280556437   0.376447725   0.075217763    0   0   0
> P        0.837980537   0.318762141   0.082724954    0   0   0
> O        0.695021832   0.151990660   0.085077236    0   0   0
> O        0.924712372   0.892977386   0.088510276    0   0   0
> O        0.829586379   0.798203506   0.091008410    0   0   0
> O        0.213810893   0.129262179   0.102459474    0   0   0
> Co       0.791263053   0.962009487   0.102731138    0   0   0
> O        0.339425748   0.722213050   0.103297569    0   0   0
> Co       0.885099923   0.081816736   0.103692754    0   0   0
> Co       0.385100377   0.581816730   0.103692776    0   0   0
> O        0.430774496   0.441420429   0.104087807    0   0   0
> Co       0.978937191   0.201623991   0.104654238    0   0   0
> O        0.556389351   0.034371300   0.104925902    0   0   0
> O        0.940613865   0.365429972   0.116376965    0   0   0
> O        0.845487883   0.270656085   0.118875129    0   0   0
> O        0.075178275   0.011642810   0.122308171    0   0   0
> P        0.932219708   0.844871338   0.124660421    0   0   0
> Co       0.489643808   0.787185753   0.132167613    0   0   0
> O        0.067214244   0.620870964   0.132740919    0   0   0
> P        0.361354279   0.006083789   0.142115621
> O        0.446802131   0.950135511   0.145110715
> O        0.214381915   0.837791409   0.146887224
> O        0.593110221   0.629859448   0.161855388
> O        0.355569602   0.519337757   0.162613913
> P        0.444333889   0.463046511   0.162481449
> O        0.733915313   0.849462282   0.171314557
> Co       0.331397450   0.684149370   0.174777754
> P        0.880835007   0.624048906   0.181575275
> O        0.729016571   0.457586972   0.184340848
> O        0.943694570   0.199413194   0.185888622
> O        0.842699539   0.103890146   0.188690045
> O        0.246376254   0.435621465   0.201025875
> Co       0.819907469   0.267437250   0.200281311
> O        0.371654672   0.028624679   0.201597106
> Co       0.919293748   0.386217687   0.198228118
> Co       0.408991643   0.881622266   0.208931455
> O        0.502982285   0.747275057   0.201700410
> Co       0.015942502   0.506736170   0.203798000
> O        0.581988259   0.338815157   0.205761317
> O        0.989082264   0.670263393   0.214923633
> O        0.891588821   0.575388161   0.217463006
> O        0.102116329   0.316952504   0.225311380
> P        0.946018990   0.150667428   0.220957196
> Co       0.509889754   0.092572883   0.231027714
> O        0.087929910   0.910622245   0.254736182
> P        0.390071467   0.310008795   0.243522265
> O        0.475452219   0.253683339   0.241349488
> O        0.235229551   0.143749020   0.238654386
> O        0.612387032   0.940393783   0.254302766
> O        0.441611912   0.824444770   0.264038723
> P        0.540200975   0.770461487   0.260363655
> O        0.761099937   0.156388759   0.269996408
> Co       0.350068981   0.991380761   0.270128489
> P        0.873321153   0.936340371   0.286294166
> O        0.833246668   0.765227606   0.276230271
> O       -0.000361722   0.500532992   0.288698932
> O        0.881119075   0.405321157   0.282221320
> O        0.360000301   0.737045056   0.298351129
> Co       0.882972312   0.575549749   0.299644501
> O        0.422605865   0.327653597   0.304586136
> Co       0.978817281   0.686215697   0.299070830
> Co       0.413208161   0.191270814   0.293687127
> O        0.508789991   0.058470538   0.306778792
> Co       0.104885226   0.777001345   0.337018699
> O        0.655258778   0.642479617   0.299146914
> O       -0.013826595   0.991404406   0.298780328
> O        0.795664337   0.914010571   0.342626007
> O        0.182057906   0.620327437   0.315087245
> P       -0.025531312   0.449691921   0.318993246
> Co       0.536676633   0.394337417   0.322803232
> O        0.111523355   0.238614584   0.330445421
> P        0.458259125   0.623697091   0.344422574
> O        0.563543106   0.565239764   0.345713118
> O        0.245933114   0.438564927   0.345886633
> O        0.755827316   0.261536514   0.398125722
> O        0.347085887   0.142061029   0.350995120
> P        0.418798485   0.087516712   0.363471914
> O        0.760091719   0.450332386   0.364446953
> Co       0.425302156   0.268828519   0.364933404
> P        1.000978059   0.228830728   0.389926937
> O        0.665322447   0.083338404   0.398947262
> O        0.175348426   0.819170270   0.393432843
> O        0.972375724   0.715594688   0.364967608
> O        0.192491280   0.055768375   0.386972733
> Co       0.947698792   0.864533921   0.380242742
> O        0.461116896   0.646777652   0.398656956
> Co      -0.128695091   0.044030025   0.349922760
> Co       0.459662371   0.500794114   0.364054027
>
>
> K_POINTS {automatic}
>   3 3 1 0 0 0
>
> CELL_PARAMETERS {alat}
>   1.000000000000d0  0.000000000000d0  0.000000000000d0
>   -0.125138500246d0  5.222389311845d0  0.000000000000d0
>   0.000000000000d0  0.000000000000d0  4.847983163860d0
>
> LIANG Xiongyi
> CIty University of Hong Kong



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: <giuseppe.mattioli at ism.cnr.it>



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