[Pw_forum] Noncollinear magnetization and spin orbit coupling problem on Energy convergence and Spin
Paolo Giannozzi
paolo.giannozzi at uniud.it
Mon Mar 3 10:47:42 CET 2014
What happens without the O2 molecule? P.
On Sat, 2014-03-01 at 19:30 +0000, Xiao Shi wrote:
> Hi Mulwa and other PW users
>
>
>
>
> Thanks for your advise. However, the same problem still happens.
>
>
> Has anyone met this kind of situation before? I'm wondering if this is
> the problem of the system or I didn't set the correct parameters.
>
>
>
>
> On Wed, 26 Feb 2014 2:56pm Winfred Mulwa <mulwawinfred at gmail.com>
> wrote
>
>
> >Try to set conv_thr = 1.0 d -4 in the namelist electrons
> >On Tue, Feb 25, 2014 at 11:41 PM, Xiao Shi <xiaos at princeton.edu>
> wrote:
> >
> >> Dear PW users
> >>
> >> I'm doing calculations on Bi2Se3 system and get some problem with
> the
> >> magnetization of this system.
> >> As Bi2Se3 is a topological insulator, I need large spin orbit
> coupling
> >> effect which means I need to do noncollinear calculation.
> >>
> >> After adding O2 molecule on the surface, I did spin polarization
> >> calculation where the energy doesn't converge and the system goes
> into
> >> anti-ferromagnetic like shown below:
> >>
> >>
> >> total energy = -5045.36386241 Ry
> >> Harris-Foulkes estimate = -5045.36391863 Ry
> >> estimated scf accuracy < 0.00001751 Ry
> >>
> >> total magnetization = -0.00 0.00 2.00 Bohr
> mag/cell
> >> absolute magnetization = 3.42 Bohr mag/cell
> >>
> >>
> >> If I continue for more steps, it will grows into very large
> >> anti-ferromagnetic like 20 Bohr mag/cell for absolute magnetization
> which
> >> is unphysical. The O2 I placed is far away from the surface and
> there
> >> shouldn't be any spin polarization for pristine surface in reality.
> Also
> >> the total energy doesn't change monotonically.
> >>
> >>
> >> The input file is listed below:
> >> This is a supercell system of Bi2Se3 with 2*2 in the hcp lattice
> and there
> >> are 15 layers of atom for the slab with vacuum larger than 20ans
> (O2 is at
> >> least 10ans away from the slab)
> >>
> >> &system
> >> ibrav=4,
> >> celldm(1)=15.992,
> >> celldm(3)=6.555356882,
> >> nat=62,
> >> ntyp=3,
> >> ecutwfc=30.0,
> >> ecutrho=300.0,
> >> occupations='smearing',
> >> degauss=0.002,
> >> noncolin=.true.,
> >> lspinorb=.true.,
> >> starting_magnetization(1)=-0.001,
> >> starting_magnetization(2)=0.001,
> >> starting_magnetization(3)=0.5,
> >> london=.true.
> >> starting_spin_angle=.true.
> >> nosym=.true.
> >> /
> >> &electrons
> >> mixing_beta=0.2
> >>
> >> ATOMIC_SPECIES
> >> Bi 208.98 Bi.rel-pbe-dn-rrkjus.UPF
> >> Se 78.96 Se.rel-pbe-n-rrkjus_psl.0.2.UPF
> >> O 16.00 O.rel-pbe-n-rrkjus_psl.0.1.UPF
> >> ATOMIC_POSITIONS {crystal}
> >> O 0.582808125 0.518307602 0.030071968
> >> O 0.438796581 0.511316952 0.033700923
> >> Se 0.333363441 0.666726883 0.270506612
> >> Se 0.333363312 0.166681597 0.270506668
> >> Se 0.833409077 0.166681597 0.270506668
> >> Se 0.833408961 0.666727129 0.270506668
> >> Bi 4E-16 3E-16 0.298539365
> >> Bi 8.34671E-08 0.500045262 0.298539398
> >> Bi 0.500045295 -2.00018E-07 0.298539398
> >> Bi 0.500045179 0.500045262 0.298539398
> >> Se 0.666727117 0.333363441 0.332477455
> >> Se 0.166681746 0.333363493 0.332477478
> >> Se 0.166681629 0.833408578 0.332477478
> >> Se 0.666726948 0.833408578 0.332477478
> >> Bi 0.333363498 0.166681691 0.366247219
> >> Bi 0.833408983 0.166681691 0.366247219
> >> Bi 0.833408867 0.666726943 0.366247219
> >> Bi 0.333363441 0.666726883 0.366247266
> >> Se 3.44477E-08 0.500045237 0.394371017
> >> Se 0.50004532 -1.51013E-07 0.394371017
> >> Se 0.500045204 0.500045237 0.394371017
> >> Se 5E-16 3E-16 0.394371148
> >> Se 0.166681762 0.333363525 0.438001919
> >> Se 0.166681646 0.833408563 0.438001919
> >> Se 0.666726916 0.833408563 0.438001919
> >> Se 0.666727117 0.333363441 0.438001924
> >> Bi 0.333363644 0.166681764 0.466101291
> >> Bi 0.83340891 0.166681764 0.466101291
> >> Bi 0.833408794 0.666726797 0.466101291
> >> Bi 0.333363441 0.666726883 0.466101294
> >> Se 5E-16 4E-16 0.5
> >> Se -1.1658E-07 0.500045162 0.5
> >> Se 0.500045395 5E-16 0.5
> >> Se 0.500045279 0.500045162 0.5
> >> Bi 0.666727117 0.333363441 0.533898706
> >> Bi 0.166681764 0.333363527 0.533898709
> >> Bi 0.166681648 0.83340856 0.533898709
> >> Bi 0.666726914 0.83340856 0.533898709
> >> Se 0.333363441 0.666726883 0.561998076
> >> Se 0.333363642 0.166681762 0.561998081
> >> Se 0.833408912 0.166681762 0.561998081
> >> Se 0.833408796 0.666726799 0.561998081
> >> Se 7E-16 5E-16 0.605628852
> >> Se -2.67539E-07 0.500045087 0.605628983
> >> Se 0.50004547 1.51013E-07 0.605628983
> >> Se 0.500045354 0.500045087 0.605628983
> >> Bi 0.666727117 0.333363441 0.633752734
> >> Bi 0.166681691 0.333363381 0.633752781
> >> Bi 0.166681575 0.833408634 0.633752781
> >> Bi 0.66672706 0.833408634 0.633752781
> >> Se 0.33336361 0.166681746 0.667522522
> >> Se 0.833408928 0.166681746 0.667522522
> >> Se 0.833408812 0.666726831 0.667522522
> >> Se 0.333363441 0.666726883 0.667522545
> >> Bi -3.16627E-07 0.500045062 0.701460602
> >> Bi 0.500045495 2.00018E-07 0.701460602
> >> Bi 0.500045379 0.500045062 0.701460602
> >> Bi 7E-16 6E-16 0.701460635
> >> Se 0.166681597 0.333363195 0.729493332
> >> Se 0.166681481 0.833408728 0.729493332
> >> Se 0.666727246 0.833408728 0.729493332
> >> Se 0.666727117 0.333363441 0.729493388
> >> K_POINTS {automatic}
> >> 3 3 1 0 0 0
> >>
> >>
> >> I wonder has any meet this problem before and can give me some
> >> suggestion on it?
> >>
> >> PS: I've tried increase degauss to 0.05Ryd and decrease
> mixing_beta to
> >> 0.05 which doesn't help
> >>
> >> Best Regard
> >>
> >> Xiao Shi
> >> Department of Chemistry
> >> Princeton University
> >>
> >>
> >>
> >>
> >>
> >> _______________________________________________
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> >> Pw_forum at pwscf.org
> >> http://pwscf.org/mailman/listinfo/pw_forum
> >>
> >
> >
> >
> >--
> >Mulwa Winfred.
> >D Phil Student, Computational Material Science Group,
> >University of Eldoret,
> >Eldoret, Kenya.
>
>
>
>
>
>
> Best
> Xiao Shi
> Department of Chemistry
> Princeton University
>
>
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--
Paolo Giannozzi, Dept. Chemistry&Physics&Environment,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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