With my interpretation problem being solved (see previous summarizing mail), I'm left with the two questions about the value and "phase" of the zigzag potentials. For clarity, I repeat here these two questions (copied from the initial post).
Thanks, Stefaan ================ I know that the Berry phase approach is the recommended way nowadays for applying an external electric field in wien2k. However, for a quick test I resorted to the old zigzag potential that is described in the usersguide, sec. 7.1. It works, but I have some questions to convince me that I'm interpreting it the right way. The test situation I try to reproduce is from this paper (https://doi.org/10.1103/PhysRevLett.101.137201), in particular this picture (https://journals.aps.org/prl/article/10.1103/PhysRevLett.101.137201/figures/1/medium ). It's a free-standing slab of bcc-Fe layers, with an electric field perpendicular to the slab. For convenience, I use only 7 Fe-monolayers (case.struct is pasted underneath). Spin orbit coupling is used, and the Fe spin moments point in the positive z-direction. This is the input I used in case.in0 (the last line triggers the electric field) : TOT XC_PBE (XC_LDA,XC_PBESOL,XC_WC,XC_MBJ,XC_REVTPSS) NR2V IFFT (R2V) 30 30 360 2.00 1 min IFFT-parameters, enhancement factor, iprint 30 1.266176 1. Question 1: The usersguide tells "The electric field (in Ry/bohr) corresponds to EFIELD/c, where c is your c lattice parameter." In my example, EFIELD=1.266176 and c=65.082193 b, hence the electric field should be 0.019455 Ry/bohr. That's 0.5 V/Angstrom. However, by comparing the dependence of the moment on the field with the paper cited above, it looks like that value for field is just half of what it should be (=the moment changed as if it were subject to a field of 1.0 V/Angstrom). When looking at the definition of the atomic unit of electric field (https://physics.nist.gov/cgi-bin/cuu/Value?auefld), I see it is defined with Hartree, not Rydberg. This factor 2 would explain it. Does someone know whether 2*EFIELD/c is the proper way to get the value of the applied electric field in WIEN2k? Question 2: It is not clear from the userguide where the extrema in the zigzagpotential are. Are they at z=0 and z=0.5, as in fig. 6 of http://dx.doi.org/10.1103/PhysRevB.63.165205 ? I assumed so, that's why the slab in my case struct is positioned around z=0.25. Adding this information to the usersguide or to the documentation in the code would be useful. (or alternatively, printing the zigzag potential as function of z by default would help too) blebleble s-o calc. M|| 0.00 0.00 1.00 P 7 99 P RELA 5.423516 5.423516 65.082193 90.000000 90.000000 90.000000 ATOM -1: X=0.00000000 Y=0.00000000 Z=0.12500000 MULT= 1 ISPLIT=-2 Fe1 NPT= 781 R0=.000050000 RMT= 2.22000 Z: 26.00000 LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000 0.0000000 1.0000000 0.0000000 0.0000000 0.0000000 1.0000000 ATOM -2: X=0.00000000 Y=0.00000000 Z=0.37500000 MULT= 1 ISPLIT=-2 Fe2 NPT= 781 R0=.000050000 RMT= 2.22000 Z: 26.00000 LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000 0.0000000 1.0000000 0.0000000 0.0000000 0.0000000 1.0000000 ATOM -3: X=0.00000000 Y=0.00000000 Z=0.20833333 MULT= 1 ISPLIT=-2 Fe3 NPT= 781 R0=.000050000 RMT= 2.22000 Z: 26.00000 LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000 0.0000000 1.0000000 0.0000000 0.0000000 0.0000000 1.0000000 ATOM -4: X=0.00000000 Y=0.00000000 Z=0.29166667 MULT= 1 ISPLIT=-2 Fe4 NPT= 781 R0=.000050000 RMT= 2.22000 Z: 26.00000 LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000 0.0000000 1.0000000 0.0000000 0.0000000 0.0000000 1.0000000 ATOM -5: X=0.50000000 Y=0.50000000 Z=0.16666667 MULT= 1 ISPLIT=-2 Fe5 NPT= 781 R0=.000050000 RMT= 2.22000 Z: 26.00000 LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000 0.0000000 1.0000000 0.0000000 0.0000000 0.0000000 1.0000000 ATOM -6: X=0.50000000 Y=0.50000000 Z=0.33333333 MULT= 1 ISPLIT=-2 Fe6 NPT= 781 R0=.000050000 RMT= 2.22000 Z: 26.00000 LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000 0.0000000 1.0000000 0.0000000 0.0000000 0.0000000 1.0000000 ATOM -7: X=0.50000000 Y=0.50000000 Z=0.25000000 MULT= 1 ISPLIT=-2 Fe7 NPT= 781 R0=.000050000 RMT= 2.22000 Z: 26.00000 LOCAL ROT MATRIX: 1.0000000 0.0000000 0.0000000 0.0000000 1.0000000 0.0000000 0.0000000 0.0000000 1.0000000 8 NUMBER OF SYMMETRY OPERATIONS
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