[Pw_forum] Spin-Orbit Calculation

[roberta pigliapochi]

Dear Ajit,
please bear in mind that I AM NOT AN EXPERT and I would instead really
appreciate comments from more experienced users. I will try to give some
advice but take it with a pinch of salt. I would also like to follow up on
this by asking:

can noncolinear calculations and DFT+U go together now?

Referring to your points:

1)the AFM initial guess is set up fine. The system might still converge to
a FM situation, though. If instead you'd rather force it to stay AFM I'd go
for 'tot_magnetization'
2)yes. You may also need to specify lda_plus_u=.true. beforehand.
3)I'd say so, and I also think that the 'angle' isn't a fixed value but
rather will be optimised during the scf. Instead if you'd prefer the two
(or total) magnetizations to be kept fixed along y I'd go for
'constrained_magnetization'
4)I think that the default 'domag' (whatever it means) is set to false,
hence there should be no need for your flag to be there. Also, 'nspin=4'
may be redundant considering that you have set 'noncolin=.true.'

hope some more hard-core expert will comment on this.

good luck (:
Roberta

Roberta Pigliapochi
PhD Student | Grey Research Group
University of Cambridge


On 8 September 2015 at 12:48, Ajit Kumar Jena <jenapsi at gmail.com> wrote:

> Dear All,
>             I wish to do a *spin-orbit calculation* of our system
> (LiFePO4) which involves iron (Fe) as a magnetic element. Her*e *I am
> providing my input variables containing the system name lists and atomic
> species.
>
> My questions are the following :
>
> 1) As it is mentioned in the input, should I consider two different types
> of spins ( up and down ) to do a anti-ferromagnetic calculation ?
> 2) The way I have incorporated Hubbard 'U' is appropriate or not ?
> 3) If I am giving the inputs in this way, will it take the starting spin
> quantization axis along Y-direction or not ?
> 4) Is there any problem if i will not include " starting_spin_angle =
> .true. " ?
>
> Any kind of help is highly appreciated. I am extremely sorry if my
> questions are very trivial.
>
> *Input*
> &system
>     ibrav=  8,
>     celldm(1) = 19.326236,
>     celldm(2) = 0.587151,
>     celldm(3) = 0.458766,
>     nat=  28,
>     ntyp= 7,
> !    nspin = 4,
>     starting_magnetization(2) = 0.7,
>     starting_magnetization(3) = -0.7,
>     ecutwfc =30.0,
>     ecutrho = 250.0,
>     occupations = 'smearing' ,
>     degauss = 0.001 ,
>     smearing = 'gaussian' ,
>     noncolin = .true.
>     lspinorb = .true.
>     starting_spin_angle = .true.
>     angle1(2) = 90.0
>     angle2(2) = 90.0
>     angle1(3) = 90.0
>     angle2(3) = 90.0
>     lda_plus_u_kind = 0,
>     Hubbard_U(2)=3.0,
>     Hubbard_U(3)=3.0,
>
> ATOMIC_SPECIES
>  Li1  6.94      Li.pbe-s-van_ak.UPF
>  Fe1  55.845    Fe.rel-pbe-spn-rrkjus_psl.0.2.1.UPF
>  Fe2  55.845    Fe.rel-pbe-spn-rrkjus_psl.0.2.1.UPF
>  P1   30.9737   P.pbe-van_ak.UPF
>  O1   15.999    O.pbe-van_ak.UPF
>  O2   15.999    O.pbe-van_ak.UPF
>  O3   15.999    O.pbe-van_ak.UPF
>
> Thanks & Regards,
> Ajit,
> IIT Madras, Chennai
>
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