mirror of https://gitlab.com/QEF/q-e.git
48 lines
2.2 KiB
Plaintext
48 lines
2.2 KiB
Plaintext
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This example shows how to calculate the Density of States (DOS)
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projected onto molecular orbitals. A typical application is that
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of a molecule adsorbed on a surface, where one would like to identify
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contributions from HOMO/LUMO states to the electronic structure (DOS
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and bands). Here we take a chain of H atoms as a model surface, with
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a H2 molecule adsorbed, and we analyze the DOS and bands in terms of
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the H2 orbitals (sigma, sigma*).
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The calculation proceeds as follows (for the meaning of the cited input
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variables see the appropriate INPUT_* file)
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1) make a self-consistent calculation for the full system, which here
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is made of a chain of H atoms and a H2 molecule. In this example,
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coordinates have been set to adjust energy levels to convenient values
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input=chainH2.scf.in, output=chainH2.scf.out).
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2) make a self-consistent calculation for the molecular part, with the
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same cell / k-point parameters as for the full system.
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(input=H2.scf.in, output=H2.scf.out).
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3) use projfwc.x to project the crystal wavefunctions on an
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orthogonalized basis set of atomic orbitals for the full system and
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the molecular part (input=chainH2.projwfc.in,H2.projwfc.in,
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output=chainH2.projwfc.out,H2.projwfc.out). The projections are saved
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in files atomic_proj.xml files to be copied from $TMP_DIR/.
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4) identify which wavefunctions of the orthogonalized basis set ot
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atomic orbitals of the full system correspond to the same set as in
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the molecular part (i.e., identify the proper range which will be
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denoted as i_atmwfc_beg_full to i_atmwfc_end_full, see outputs of
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step 3).
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5) run molecularpdos.x providing in input the location of the
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atomic_proj.xml files for the full system and of the molecular
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part, and the ranges of atomic orbitals to be used
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(input=chainH2_onto_H2.in, output=chainH2_onto_H2.out).
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6) do k-resolved analysis. Perform bands calculation with pw.x for
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both the interacting system and the molecule.
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Then repeat steps 3-4 with projwfc.x option kresolveddos=.true.
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and step 5 with the same kresolveddos=.true. in molecularpdos.x
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7) if gnuplot is available, results are plotted to file
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project_chainH2_onto_H2.ps which shows projection of the DOS of the
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combined system on sigma and sigma* orbitals of the H2 molecule.
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