mirror of https://gitlab.com/QEF/q-e.git
34 lines
1.9 KiB
Plaintext
34 lines
1.9 KiB
Plaintext
To have 'better' projector in LDA+U calculations some localized Wannier functions of
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the relevant bands around the Fermi energy can be used. See for instance N.Marzari
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and D.Vanderbilt, PRB 56, 12847 (1997) and I. Sousa, N. Marzari, and
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D.Vanderbilt, PRB 65, 035109 (2001) for the definition and construction
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of Maximally Localized Wannier Functions (MLWF).
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Although it is possible to generate MLWF with the software distributed by
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Nicola Marzari at www.wannier.org, here we follow a simpler prescription
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and fix the phase-factor freedom---intrinsic in any Wannier function
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determination---in a sub-optimal but simple way using the atomic
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wavefunction as a guide.
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This is done as a post-processing step with a poormanwannier tool (pmw.x)
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that reads atomic wavefunctions and band structure of an LDA calculation
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and replaces the atomic wavefunctions with our simple Wannier functions.
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The subsequent LDA+U calculation is performed specifying in the system
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namelist U_projection_type='file' so that the freshly produced Wannier
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functions are used in the projection.
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The outcome of this calculation is an insulating state with d-level
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occupations really close to 0 or 1.
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In addition to this, the example shows how to obtain fat bands (i.e., band
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structures "weighted" by the overlap with atomic wave functions) and thereby
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identify which bands have the largest content of, e.g., Fe 3d-character.
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A non-self consistent calculation is used to compute the band structure along
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a path in the Brillouin zone, followed by the calculation of the projections
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onto atomic orbitals (projwfc.x) and the band symmetry analysis (bands.x).
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The small utility plotband.x combines those data and produces band structure
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plots with an additional third column containing the weight on the selected
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wavefunction (or the sum, if more than one is specified). In this case, the
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projections onto the 10 atomic 3d wavefunctions of the two Fe are summed up.
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