Any suggestions for the above post? Thanks for your time!
Regards Sai ------------------------------ Sai Ramadugu University of Iowa, Iowa City, USA On Mon, Dec 29, 2014 at 4:55 PM, Sai Kumar Ramadugu <[email protected]> wrote: > Dear QE Users, > > > I'm confused about how the projwfc.x does the projection to produce PDOS > plots. > > I'm running the calculations of bulk magnetite Fe3O4. It has two ways to > set up the > > structure: cubic (ibrav = 1, with 56 atoms) cell and hexagonal (ibrav = 4, > with 42 > > atoms) cell. I did PDOS calculation for both of them and checked different > d-orbital > > components (eg: dz2 and dx2-y2, and t2g: dxy, dxz and dyz) for octahedral > Fe. I found > > the five different d-orbital distributions are very different for the same > type of Fe. > > > The PDOS of different d-orbitals of octahedral Fe in Fe3O4 cubic cell > shows perfect, > > classical textbook-style octahedral crystal field splitting, where dz2 and > dx2-y2 are > > degenerate and dxy, dxz and dyz are degenerate. And their energy levels > also match > > theoretical bonding, nonbonding and antibonding model. > > > However, the PDOS of different d-orbitals of octahedral Fe in Fe3O4 > hexagonal cell > > is much more complicated than the cubic one. None of the d-orbitals are > degenerate. > > Although I can tell that their total d-orbital distribution must be the > same with the one > > we got from the cubic cell, the "dz2, dx2-y2, dxy, dxz and dyz" here are > NOT the "real > > ones" that we expected to see as those in cubic case. For example, a peak > that is > > supposed to be only contributed by dz2 or dx2-y2 (eg) orbital, is a > mixture of all the five > > d-orbitals. So now we can't get the correct d-orbital eg and t2g > occupancies in > > hexagonal cell. > > > I'm thinking why different cell type can make such big difference in PDOS > distributions. > > I guess the "x, y, z" directions defined by projwfc.x in PDOS projection > is "cell vector- > > dependent". In cubic Fe3O4, all the six Fe-O bonds around octahedral Fe > are parallel > > to one of the a, b and c cell vectors. So the "x, y, z" in PDOS projection > happen to be the > > same with the "x, y, z" in Fe crystal field splitting. But in hexagonal > Fe3O4, all of the > > octahedral Fe-O bonds are off the cell vectors. So the default "x, y, z" > in projection are no > > longer the same as those that we are looking for on octahedral Fe sites. > > > So now I'm thinking how to change the way the projwfc.x does the > projection. Because > > Fe3O4 is just a test for us. We are actually focusing on hematite Fe2O3, > which can only > > be presented by hexagonal (or rhombohedral) cell where all the Fe-O are > off the cell > > vectors. I found that there is something wrong with the eg and t2g PDOS > but don't know > > how to correct it. There seems to be a file called ".../flib/ylmr2.f90". > Is this the one > > controlling projection directions? Or is there any other way that we can > let projwfc.x does > > the PDOS projection along the directions that we really want? > > > I am attaching the figures of pdos calculations for cubic Fe3O4 and > hexagonal Fe3O4. > > > Any suggestions are welcome. > > > Thank you, > > > ---------------------------- > > Sai Ramadugu > > University of Iowa >
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