Dear all, I am giving the linear response method for Hubbard U and Hund J another go. A recent publication has obtained quite resonable values for U and J based on a hexahydrated transition metal model and I thought it might be worthwhile trying ( https://journals.aps.org/prb/abstract/10.1103/PhysRevB.98.235157) ; however, either I am too stupid or there is a bug in the Hubbard_beta routine that I cannot figure out. Anyways, if someone else has managed to do this please do comment!
The procedure should be easy, I make a series of calculation for values of Hubbard_beta keeping Hubbard_U and Hubbard_alpha=1D-40; the on-site magnetization is define by m=n(up)-n(down) which I can get from the scf output bare response: --- enter write_ns --- LDA+U parameters: U( 3) = 0.00000000 J0( 3) = 0.00000000 alpha( 3) = 0.00000000 beta( 3) = 0.05000000 atom 1 Tr[ns(na)] (up, down, total) = *4.95101* *1.38740* 6.33841 converged response atom 1 Tr[ns(na)] (up, down, total) = *4.95032* *1.39090* 6.34122 If I do this for a series of calculations I obtain the following: # beta bare conv -0.08 3.57155 3.57023 -0.05 3.56860 3.56776 -0.02 3.56561 3.56528 0.02 3.56160 3.56194 0.05 3.55856 3.55942 0.08 3.55548 3.55686 # slopes: bare= -0.100419 conv= -0.0835161 the respective \partial m/\partial \beta look linear in the region of the chosen Hubbard_beta. but the resulting J=-2*(bare^-1-conv^-1) makes no sense and even the sign is wrong. The value for Hubbard_U obtained by this method using \partial n/\partial \alpha is around 5.4, which seems perfectly suitable by the way. Input for a single calculation is attached below. Thanks for your help in advance! Chris &CONTROL calculation = "scf", ... / &SYSTEM ibrav=1,A=15.000000,ecutwfc=30, ecutrho=400, starting_magnetization(3)=0.7, nspin=2,occupations="fixed", tot_magnetization=4.000000 nat=19,ntyp=3,tot_charge=2.000000 lda_plus_U=.true.,U_projection_type="ortho-atomic" Hubbard_U(3)=1D-40,Hubbard_alpha(3)=1D-40, Hubbard_beta(3)=-0.08 / &ELECTRONS startingwfc="file", startingpot="file" mixing_beta=0.6,conv_thr=1D-12,diago_thr_init=1D-14,electron_maxstep=150, mixing_mode="local-TF" / ATOMIC_SPECIES H 1.008 H.pbe-kjpaw_psl.1.0.0.UPF O 15.999 O.pbe-n-kjpaw_psl.1.0.0.UPF Fe1 55.845 Fe.pbe-spn-kjpaw_psl.0.2.1.UPF ATOMIC_POSITIONS (angstrom) Fe1 7.500000000 7.500000000 7.500000000 O 7.500000000 7.500000000 9.491812807 O 7.500000000 9.491814995 7.500000000 O 9.491776410 7.500000000 7.500000000 O 5.508226144 7.500000000 7.500000000 O 7.500000000 5.508190791 7.500000000 O 7.500000000 7.500000000 5.508184515 H 6.674174667 10.066164672 7.500000000 H 8.326002124 10.065917296 7.500000000 H 10.065724550 7.500000000 8.326098474 H 10.066137163 7.500000000 6.674195836 H 7.500000000 6.674283010 4.933686902 H 7.500000000 8.326129049 4.934261135 H 6.674236823 4.933772022 7.500000000 H 8.326063477 4.934192685 7.500000000 H 4.934274010 7.500000000 6.673909845 H 4.933876539 7.500000000 8.325806755 H 7.500000000 6.674482948 10.066592251 H 7.500000000 8.326364525 10.065407565 K_POINTS (automatic) 1 1 1 0 0 0 -- Postdoctoral Researcher Center for Quantum Nanoscience, Institute for Basic Science Ewha Womans University, Seoul, South Korea
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