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<div style="direction: ltr;font-family: Tahoma;color: #000000;font-size: 10pt;">Dear PW users
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<div>I'm doing calculations on Bi2Se3 system and get some problem with the magnetization of this system.</div>
<div>As Bi2Se3 is a topological insulator, I need large spin orbit coupling effect which means I need to do noncollinear calculation.</div>
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<div>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:</div>
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<div> total energy = -5045.36386241 Ry</div>
<div> Harris-Foulkes estimate = -5045.36391863 Ry</div>
<div> estimated scf accuracy < 0.00001751 Ry</div>
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<div> total magnetization = -0.00 0.00 2.00 Bohr mag/cell</div>
<div> absolute magnetization = 3.42 Bohr mag/cell</div>
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<div>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.</div>
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<div>The input file is listed below:</div>
<div>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)</div>
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<div> &system</div>
<div> ibrav=4,</div>
<div> celldm(1)=15.992,</div>
<div> celldm(3)=6.555356882,</div>
<div> nat=62,</div>
<div> ntyp=3,</div>
<div> ecutwfc=30.0,</div>
<div> ecutrho=300.0,</div>
<div> occupations='smearing',</div>
<div> degauss=0.002,</div>
<div> noncolin=.true.,</div>
<div> lspinorb=.true.,</div>
<div> starting_magnetization(1)=-0.001,</div>
<div> starting_magnetization(2)=0.001,</div>
<div> starting_magnetization(3)=0.5,</div>
<div> london=.true.</div>
<div> starting_spin_angle=.true.</div>
<div> nosym=.true.</div>
<div> /</div>
<div> &electrons</div>
<div> mixing_beta=0.2</div>
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<div>ATOMIC_SPECIES</div>
<div> Bi 208.98 Bi.rel-pbe-dn-rrkjus.UPF</div>
<div> Se 78.96 Se.rel-pbe-n-rrkjus_psl.0.2.UPF</div>
<div> O 16.00 O.rel-pbe-n-rrkjus_psl.0.1.UPF</div>
<div>ATOMIC_POSITIONS {crystal}</div>
<div>O 0.582808125 0.518307602 0.030071968</div>
<div>O 0.438796581 0.511316952 0.033700923</div>
<div>Se 0.333363441 0.666726883 0.270506612</div>
<div>Se 0.333363312 0.166681597 0.270506668</div>
<div>Se 0.833409077 0.166681597 0.270506668</div>
<div>Se 0.833408961 0.666727129 0.270506668</div>
<div>Bi 4E-16 3E-16 0.298539365</div>
<div>Bi 8.34671E-08 0.500045262 0.298539398</div>
<div>Bi 0.500045295 -2.00018E-07 0.298539398</div>
<div>Bi 0.500045179 0.500045262 0.298539398</div>
<div>Se 0.666727117 0.333363441 0.332477455</div>
<div>Se 0.166681746 0.333363493 0.332477478</div>
<div>Se 0.166681629 0.833408578 0.332477478</div>
<div>Se 0.666726948 0.833408578 0.332477478</div>
<div>Bi 0.333363498 0.166681691 0.366247219</div>
<div>Bi 0.833408983 0.166681691 0.366247219</div>
<div>Bi 0.833408867 0.666726943 0.366247219</div>
<div>Bi 0.333363441 0.666726883 0.366247266</div>
<div>Se 3.44477E-08 0.500045237 0.394371017</div>
<div>Se 0.50004532 -1.51013E-07 0.394371017</div>
<div>Se 0.500045204 0.500045237 0.394371017</div>
<div>Se 5E-16 3E-16 0.394371148</div>
<div>Se 0.166681762 0.333363525 0.438001919</div>
<div>Se 0.166681646 0.833408563 0.438001919</div>
<div>Se 0.666726916 0.833408563 0.438001919</div>
<div>Se 0.666727117 0.333363441 0.438001924</div>
<div>Bi 0.333363644 0.166681764 0.466101291</div>
<div>Bi 0.83340891 0.166681764 0.466101291</div>
<div>Bi 0.833408794 0.666726797 0.466101291</div>
<div>Bi 0.333363441 0.666726883 0.466101294</div>
<div>Se 5E-16 4E-16 0.5</div>
<div>Se -1.1658E-07 0.500045162 0.5</div>
<div>Se 0.500045395 5E-16 0.5</div>
<div>Se 0.500045279 0.500045162 0.5</div>
<div>Bi 0.666727117 0.333363441 0.533898706</div>
<div>Bi 0.166681764 0.333363527 0.533898709</div>
<div>Bi 0.166681648 0.83340856 0.533898709</div>
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<div>Bi 0.666726914 0.83340856 0.533898709</div>
<div>Se 0.333363441 0.666726883 0.561998076</div>
<div>Se 0.333363642 0.166681762 0.561998081</div>
<div>Se 0.833408912 0.166681762 0.561998081</div>
<div>Se 0.833408796 0.666726799 0.561998081</div>
<div>Se 7E-16 5E-16 0.605628852</div>
<div>Se -2.67539E-07 0.500045087 0.605628983</div>
<div>Se 0.50004547 1.51013E-07 0.605628983</div>
<div>Se 0.500045354 0.500045087 0.605628983</div>
<div>Bi 0.666727117 0.333363441 0.633752734</div>
<div>Bi 0.166681691 0.333363381 0.633752781</div>
<div>Bi 0.166681575 0.833408634 0.633752781</div>
<div>Bi 0.66672706 0.833408634 0.633752781</div>
<div>Se 0.33336361 0.166681746 0.667522522</div>
<div>Se 0.833408928 0.166681746 0.667522522</div>
<div>Se 0.833408812 0.666726831 0.667522522</div>
<div>Se 0.333363441 0.666726883 0.667522545</div>
<div>Bi -3.16627E-07 0.500045062 0.701460602</div>
<div>Bi 0.500045495 2.00018E-07 0.701460602</div>
<div>Bi 0.500045379 0.500045062 0.701460602</div>
<div>Bi 7E-16 6E-16 0.701460635</div>
<div>Se 0.166681597 0.333363195 0.729493332</div>
<div>Se 0.166681481 0.833408728 0.729493332</div>
<div>Se 0.666727246 0.833408728 0.729493332</div>
<div>Se 0.666727117 0.333363441 0.729493388</div>
<div>K_POINTS {automatic}</div>
<div>3 3 1 0 0 0</div>
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<div>I wonder has any meet this problem before and can give me some suggestion on it?</div>
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<div>PS: I've tried increase degauss to 0.05Ryd and decrease mixing_beta to 0.05 which doesn't help</div>
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<div>Best Regard</div>
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<div>Xiao Shi</div>
<div>Department of Chemistry</div>
<div>Princeton University</div>
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