Top Page > Browsing

Spin-orbit interaction and electron structure in NCDFT Date: 2017/10/25 05:43 Name: Daniil Dear developers, We are trying to reproduce the atomic state of Niobium with the OpenMX package. However, it seems that the spin-orbit interaction does not work like expected. For comparison, we performed 4 calculations: with two programs (openmx and turbomole) with and without spin-orbit interaction for each case. We used default VPS and PAO for openmx calculations, and our pseudopotential and basis for turbomole. (We also tried our pseudopotential and basis embedded in openmx format, and results were quite close to the default ones). Both programs gave similar results in case of no so-interaction, but when the latter was enabled, in both programs orbital energies were split, but only in turbomole it resulted in change of electron distribution. 1. We calculated LJ-occupancies and for d-electrons results are: |D,1.5> 1.60 |D,2.5> 2.40 for openmx-noso, openmx-so and turbomole-noso, and |D,1.5> 1.74 |D,2.5> 2.26 for turbomole-so 2. We compared spin density (or "magnetization" for turbomole) cube files, and they were of exact cubic symmetry for openmx-noso, openmx-so and turbomole-noso and distorted for turbomole-so. So, the question is if it is possible to achieve the change of electronic distribution in OpenMX with spin-orbit interaction enabled? All essential files, including cube files and images are shared at the https://www.dropbox.com/sh/0zhe2jq3bwpkz7g/AAAYVVA1aUk_YSA9oTA1I_oZa?dl=0 folder. dm_ljm.mat file is density matrix, converted to N/L/J/MJ basis. Best regards, Daniil

Page: [1]

Re: Spin-orbit interaction and electron structure in NCDFT ( No.1 ) Date: 2018/01/07 07:48 Name: Daniil Hi, Any information or advices about this case? Best regards, Daniil Re: Spin-orbit interaction and electron structure in NCDFT ( No.2 ) Date: 2018/01/08 13:36 Name: Chi-Cheng Lee  <cclee.physics@gmail.com> Hi Daniil, From a user's point of view, I guess the default energy cutoff is too small to give a noticeable distorted charge density from the cubic one. The charge density could also not converge very well. This might not be due to the difference between openmx and turbomole. Could you try to add the following parameter? scf.energycutoff 200 and also try to change 200 to 300, 400, or 500 to see if there is any difference in the spin density? For me, I would also add Atoms.UnitVectors.Unit Ang <Atoms.UnitVectors 10 0 0 0 10 0 0 0 10 Atoms.UnitVectors> to specify the unit cell size and I will also set k point to 1 1 1, such as scf.Kgrid 1 1 1 to save time. Cheers, Chi-Cheng Re: Spin-orbit interaction and electron structure in NCDFT ( No.3 ) Date: 2018/01/08 14:43 Name: T. Ozaki Hi, I checked "nb.out" and "nb.sden.cube" stored in "openmx-so", and found that the charge distribution deviates from the cubic one. It can be seen that the Mulliken populations violate the cubic symmetry. In addition to this, if you carefully look at isosurface of the cube file, the distribution looks like tetragonal rather than cubic, while "nb.sden.cube" stored in "openmx-noso" remains cubic. Also, please be careful that there is freedom in the distribution due to degeneracy of the spin-orbit states, which may cause the difference between OpenMX and TURBOMOLE. Regards, TO Re: Spin-orbit interaction and electron structure in NCDFT ( No.4 ) Date: 2018/01/16 04:52 Name: Daniil Thank you for answers. I tried to increase scf.energycutoff, but with only small, if any, effect. Yes, under close study cube files are slightly distorted from cubic symmetry, but much less than in turbomole case. As for LJ-distribution: Correct me, if I am wrong, but in first order, SO interaction is proportional to l*s, so that degeneracy between j=l±s states should disappear. Thus, electrons must redistribute, which can be seen in case of Turbomole calculations: initial non-so distribution is 1.6:2.4 = 4:6, where 4 and 6 are total numbers of j=1.5 and j=2.5 states for D-shell, while under SO interaction j=1.5 states become lower by energy and their total occupation increases to 1.74. Best regards, Daniil Re: Spin-orbit interaction and electron structure in NCDFT ( No.5 ) Date: 2018/03/05 23:48 Name: Daniil Hi, Can you please comment on LJ-distribution? The D1/3-D3/2 degeneracy should vanish with SO enabled. Best regards, Daniil Re: Spin-orbit interaction and electron structure in NCDFT ( No.6 ) Date: 2018/03/23 00:44 Name: T. Ozaki Hi, In OpenMX the population of each state is determined by the Fermi-Dirac function, which is not a proper treatment for an isolate system like atom especially with a high temperature. With the spin-orbit coupling I found that the populations vary depending on the electronic temperature as follows: At 10 K spin up spin down d3z^2-r^2 0 0.370180785 0.001097401 dx^2-y^2 0 0.826992544 0.000216028 dxy 0 0.802166556 0.000220739 dxz 0 0.999197203 0.000354755 dyz 0 0.999197364 0.000354753 sum over m 3.997734451 0.002243677 At 300 K d3z^2-r^2 0 0.822098488 0.000719802 dx^2-y^2 0 0.789486124 0.000154999 dxy 0 0.769269179 0.000157835 dxz 0 0.808441550 0.000555007 dyz 0 0.808446917 0.000555006 sum over m 3.997742258 0.002142649 This would be responsible for the problem. Regards, TO Re: Spin-orbit interaction and electron structure in NCDFT ( No.7 ) Date: 2018/03/24 07:15 Name: Daniil Thanks for your explanation. I tried to perform low-temperature calculations, but scf seems to be very unstable with 10K. How did you achieve convergence? I tried to increase scf.Mixing.History and scf.Mixing.StartPulay, but with no effect. And are there any other drawbacks to using low temperature, except for scf instability? Best regards, Daniil Re: Spin-orbit interaction and electron structure in NCDFT ( No.8 ) Date: 2018/03/24 09:09 Name: T. Ozaki Hi, The following is a set of parameters I used: scf.XcType GGA-PBE # LDA|LSDA scf.SpinOrbit.Coupling on scf.SpinPolarization NC # On|Off scf.maxIter 300 # default=40 scf.ElectronicTemperature 10.0 # default=300 (K) scf.energycutoff 1000.0 # default=150 (Ry) scf.EigenvalueSolver Cluster # Recursion|Cluster|Band scf.Kgrid 1 1 1 # means 4x4x4 scf.Mixing.Type rmm-diish # Simple|Rmm-Diis|Gr-Pulay|Kerker|Rmm-Diisk scf.Init.Mixing.Weight 0.01 # default=0.30 scf.Min.Mixing.Weight 0.001 # default=0.001 scf.Max.Mixing.Weight 0.200 # default=0.40 scf.Mixing.History 20 # default=5 scf.Mixing.StartPulay 15 # default=6 scf.criterion 1.0e-8 # default=1.0e-6 (Hartree) Regards, TO Re: Spin-orbit interaction and electron structure in NCDFT ( No.9 ) Date: 2018/03/24 21:30 Name: Daniil Thanks! With your parameters, calculation did converge, with occupations similar to yours: d3z^2-r^2 0 0.365803842 0.001118400 0.366922242 0.364685441 0.0004 -37.0934 dx^2-y^2 0 0.829987864 0.000217503 0.830205368 0.829770361 0.0004 -35.8720 dxy 0 0.803548928 0.000222626 0.803771554 0.803326302 0.0004 -35.8685 dxz 0 0.999177628 0.000357497 0.999535125 0.998820132 0.0005 -34.0179 dyz 0 0.999177633 0.000357496 0.999535129 0.998820136 0.0005 -37.1983 sum over m 3.997695895 0.002273522 3.999969417 3.995422373 But, unfortunately, it still yielded 1.6/2.4 ratio for d-electrons. Best regards, Daniil Re: Spin-orbit interaction and electron structure in NCDFT ( No.10 ) Date: 2018/04/19 04:02 Name: Daniil Hi, Is it possible to perform 0K calculations in OpenMX? I tried to increase scf parameters, but convergence was not achieved yet. So, does it make sense to continue, or there are some fundamental restrictions in scf algorithms? Best regards, Daniil

Page: [1]