[Wien] Problems of HCP Tb!!! (the second time)
Hui Wang
hwang at imr.ac.cn
Sat Jan 30 13:23:32 CET 2010
Dear wien users:
First, thank you so much for Stefaan's detailed reply, I really appreciate. After adopting Stefaan's suggestions, my problems are as follows:
case.struct, case.in1, case.in2, case.inm are the same as last time.
The reason I use kpoints = 1000 is because I refered to S. Cottenier's book ---Density Functional Theory and the Family of (L)APW-methods: a step-by-step introduction, it uses kpoints = 912 for hcp-Cd (its lattice constant(bohr) is 5.630252 5.630252 10.617619 90.000000 90.000000120.000000). The primitive cell volume of HCP Tb is a little bigger than HCP Cd, so I think using kpoints = 1000 is reasonable. I also use kpoints = 4000 for HCP Tb, the total energy only changed 0.4 mRy, so kpoints = 1000 is enough.
According to Stefaan's suggestions, I recalculate HCP Tb. ( Userguide says first use +SO, then use +U in page 85 of 2009's userguide.)
order: GGA==>>GGA+SO==>>GGA+SO+U
(1)run a regular GGA scf, commamd line: runsp -ec 0.0001 -cc 0.0001 -i 1000
then i got some results as follows:
:ENE: -46876.362493 Ry
:MMTOT: 12.01107 uB
:MMI001: 5.86470 uB
:MMINT: 0.28167 uB
(2)based on the GGA scf, i added the spin-orbit coupling.
case.indmc, case.inso and case.inorb were prepared as follows:
case.indmc
*************************************************************
-9. Emin cutoff energy
1 number of atoms for which density matrix is calculated
1 1 3 index of 1st atom, number of L's, L1
0 0 r-index, (l,s)index
*************************************************************
case.inorb
*************************************************************
1 1 0 nmod, natorb, ipr
PRATT 1.0 BROYD/PRATT, mixing
1 1 3 iatom nlorb, lorb
1 nsic 0..AFM, 1..SIC, 2..HFM
0.50 0.00 U J (Ry) Note: we recommend to use U_eff = U-J and J=0
*************************************************************
case.inso
*************************************************************
WFFIL
4 1 0 llmax,ipr,kpot
-9.0000 2.0000 emin,emax (output energy window)
0. 0. 1. direction of magnetization (lattice vectors)
1 number of atoms for which RLO is added
1 -1.7 0.01 atom number,e-lo,de (case.in1), repeat NX times
0 0 0 0 0 number of atoms for which SO is switch off; atoms
*************************************************************
run a regular GGA+SO scf, commamd line: runsp -ec 0.0001 -cc 0.0001 -so -i 1000
then i got some results as follows:
:ENE: -46876.608343 Ry
:MMTOT: 11.92563 uB
:MMI001: 5.81891 uB
:MMINT: 0.28781 uB
I added spin orbit coupling, but there is no :ORB information, i don't why ?
(3)based on the GGA+SO scf, then i added the U parameter.
case.inorb and case.indm were prepared as follows:
case.indm
*************************************************************
-9. Emin cutoff energy
1 number of atoms for which density matrix is calculated
1 1 3 index of 1st atom, number of L's, L1
0 0 r-index, (l,s)index
*************************************************************
case.inorb
*************************************************************
1 1 0 nmod, natorb, ipr
PRATT 1.0 BROYD/PRATT, mixing
1 1 3 iatom nlorb, lorb
1 nsic 0..AFM, 1..SIC, 2..HFM
0.50 0.00 U J (Ry) Note: we recommend to use U_eff = U-J and J=0
*************************************************************
run a regular GGA+SO scf, commamd line: runsp -ec 0.0001 -cc 0.0001 -so -orb -i 1000
then i got some results as follows:
:ENE: -46876.47444 Ry
:MMTOT: 13.45593 uB
:MMI001: 6.25394 uB
:MMINT: 0.94806 uB
:ORB001: 0.00439 uB ( I don't know why it is so small ?)
After the three steps above, and also according to Stefaan's suggestions ,I changed the last line of case.indmc from '0 0' to '1 3' after convergence,
case.indmc
*************************************************************
-9. Emin cutoff energy
1 number of atoms for which density matrix is calculated
1 1 3 index of 1st atom, number of L's, L1
1 3 r-index, (l,s)index
*************************************************************
then I run 'x lapwdm -c -so -up', and I find the orbital moment in case.scfdmup is as follows:
case.scfdmup
*************************************************************
Spin-polarized + s-o calculation, M|| 0.000 0.000 1.000
Calculation of <X>, X=c*Xr(r)*Xls(l,s)
Xr(r) = I
Xls(l,s) = L(dzeta)
c= 1.00000
atom L up dn total
:XOP 1 3 -0.00187 0.00626 0.00439
*************************************************************
The orbital moment is only 0.00439, I was abosolutely confused.
In a word, although I adopt Stefaan's suggestion, and maybe I took it in the wrong way or I didn't understand Stefaan's suggestion well, the calculated total magnetic moment of single Tb atom is still too small, comparing with the experimental magnetic moment 10 uB.
So my questions are as follows:
(1)What's my problem? I have been puzzled by this for almost a month, this question is the most important one. If your time permiting, can anyone give me a detailed reply(step by step will be greatly appreciated) about how to correctly calculate the total magnetic moment of single Tb atom ?
(2)Is there any diffenece about the priority order of +SO and +U ? ( userguide page 85 says: first +SO,then +U) Some systems don't have spin-orbit coupling.
(3)What the difference between case.indm and case.indmc ? In my case, the content of them are exactly same, just the name is different. (I already know case.indmc is for spin orbit coupling, and case.indm is for GGA+U)
(4)I saw a mailing list which was answered by Stefaan, it said: Convergence with LDA+U might be problematic, that often happens.Converge with LDA first, then save_lapw. Now converge with -orbc, then save_lapw. Finally do unconstrained LDA+U (-orb). If it doesn't work even that way, then consider to crank up the U slowly (first 0.1,converge, save, then 0.2, etc.)
My question is : when should use -orbc, and when to use -orb ? In my case, I just use -orb.
(5)Stefaan told me that: you have to change the last line to '1 3' after convergence, and run 'x lapwdm -c -so -up' to find the orbital moment in case.scfdmup. My question is when to change '0 0' to '1 3' in case.indmc ?
(6)Do you think it is very important to use Hybrid Functionals in HCP Tb system ?
I am so sorry to bring you to so much trouble, but I really need your help to deal with HCP Tb which puzzled me for almost a month. Your kindly help will be greatly appreciated.
Anyway, thanks a lot for the suggestion of Stefaan, really.
I am looking forward to your reply.
Cheers.
Yours sincerely
Hui Wang
=========================================================
Magnetism and Magnetic Materials Division
Shenyang Materials Science National Laboratory
Institute of Metal Research
Chinese Academy of Sciences
72 Wenhua Road, Shenyang 110016, P. R. China
Tel: +86-24-83978845
PHD: Wanghui
Email: hwang at imr.ac.cn
=========================================================
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