Dear Wien2k users and developers, I would be grateful for your opinion about a somewhat peculiar behavior I am getting.
I calculate the electronic structure of the beta phase of uranium hydride (UH3). It has a cubic primitive cell with 8 formula units in it. There are two nonequivalent U positions, one with multiplicity 2 (site 2a, higher symmetry, Th), the other with multiplicity 6 (site 6c, lower symmetry, D2d), struct file is attached. I run a spin-polarized calculation (PBE) with spin-orbit coupling and direction of magnetization 111 (struct file with the lowered symmetry is also attached). Then I calculate the orbital (and spin) moments using LAPWDM (the resulting case.scfdmup is attached). For the uranium site with multiplicity 2 I get moments along 111 as expected but for the lower-symmetry site the direction deviates from 111 for the orbital as well as spin moment. In particular, for the f shell I get mS = ( 1.21, 1.16, 1.16 ) = (mx,my,mz), mL = -( 1.42, 1.18, 1.18 ). Now to my questions: a) Is this a valid result or is such non-collinearity a sign of something being broken? b) In particular, is this (local) moment deviating from 111 compatible with the assumption of SYMMETSO (magnetization along 111)? c) If the result is valid, would I get the moments at the individual 6c sites by applying the rotation matrices ROTIJ to the moments returned by LAPWDM? c') Side question: Are these ROTIJ matrices printed out somewhere? I get them by uncommenting a few lines in SRC_lapw1/atpar.F. An analogous behavior was recently reported in https://doi.org/10.1016/j.jnucmat.2022.153817 using PBE+U in VASP. When I do the rotations suggested in c) above, I reconstruct the pattern shown in Table 3 of the linked reference. When the moments of all the equivalent 6c sites are added together, the resulting moment points along 111 so that the total magnetization has the direction as assumed at the beginning. That may mean that c) makes sense but I am not sure. Best regards Jindrich Kolorenc
b-UH3.struct
Description: Binary data
b-UH3FM111.struct
Description: Binary data
b-UH3FM111.scfdmup.dm
Description: Binary data
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