mirror of https://gitlab.com/QEF/q-e.git
49 lines
2.1 KiB
Plaintext
49 lines
2.1 KiB
Plaintext
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This example shows how to use QE to apply the dipole field correction in two
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different cases, first a Ni metal slab with a adsorbed CO molecule and second
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a water molecule in vacuum.
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Note about the dipole field correction.
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-----
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In several cases the electron configuration of the grund state in a
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SCF calculation generates a macroscopic dipole in the cell. This effect
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will influence the slope of the potential far away from the atoms, in
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the vacuum region. To correct this dipole effect and let the potential
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recover a constant level (the vacuum level) far away from the atoms it's
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possible to correct the SCF potential by introducing a electric double
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layer in the vacuum region which generates an electric field that cancels
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the macroscopic dipole in the slab. (See Bengtsson PRB 59, 12 301 (1999)
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and Meyer and Vanderbilt, PRB 63, 205426 (2001).)
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To launch a calculation with the dipole correction it's important to define the
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correct position (and obviously the direction) where to insert the compensating
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eletric double layer, a vacuum region where almost no charge is present.
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----
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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 Ni+CO slab (input=ni+co.scf,
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output=ni+co.scf.out). Emaxpos, eopreg and edir are the essential
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variables needed to define position and width of electric double
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layer giving the dipole correction.
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2) extract the total electrostatic potential (V_bare + V_H potential)
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with a post-process run (input=ni+co.pp.in, output=ni+co.pp.out,
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potential_file=ni+co.vpot).
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3) calculate the planar average along the edir direction and plot the result
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(input=ni+co.avg.in, output=ni+co.vpot-z, plot=ni+co.eps).
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4) make a self-consistent calculation for water molecule (input=water.scf,
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output=water.scf.out).
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5) extract the potential (the V_bare + V_H potential) with a post-process run
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(input=water.pp.in, output=water.pp.out, potential_file=water.vpot).
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5) calculate the planar average along the edir direction and plot the result
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(input=water.avg.in, output=water.vpot-z, plot=water.eps).
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