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Cu_slab: 2-dim. Periodic System
Sample directory: band/e_Cu_slab/
A two-dimensional infinite (periodic boundary conditions)
slab calculation is performed for Cu. The dimensionality is simply defined by
the number of records in the Lattice data block.
In a 2-dimensional calculation the lattice vectors are put in the xy-plane. (In
a one-dimensional calculation (polymer), the lattice vector is taken along the
x-axis in the program.)
In this example, the minimal numerical basis from the DIRAC
subprogram is augmented by Slater-type orbital basis functions, with the
keyword BasisFunctions.
Slab calculations for metals frequently suffer from SCF
convergence problems, as a result of the open valence band(s). To help the
program converge it is often useful or even necessary to use some special
features, such as the AllBands key. This
particular key requires a numerical value (0.025 in the example) and implies
that a finite-temperature electronic distribution is used, rather than a sharp
cut-off at the Fermi level. The numerical value is the applied energy width, in
hartree units.
The so-modified electronic distribution also affects the
energy. The 'true' zero-T energy is computed, approximately, by an
interpolation formula. The interpolation is not very accurate and one should
try to use as small as possible values for the AllBands
key so as to avoid increasing uncertainty in the results. The program prints,
in the energy section of the output file, the finite-T correction term that has
been applied through the interpolation formula. This gives at least an
indication of any remaining uncorrected deviation of the outcome from a true
zero-T calculation.
$ADFBIN/band << eor
Title Cu slab
Comment
Technical
Quadratic K space integration
Good real space integration accuracy
Features
Lattice : 2D
Unit cell : 1 atom, 1x1
Basis : NO+STO w/ core
Options : AllBands (temperature effect)
End
MaxMemoryUsage=20
Kspace 5
Accuracy 4
Convergence
AllBands 0.025
End
Lattice
4.822 0.0
0.0 4.822
End
Atoms Cu
0.0 0.0 0.0
End
AtomType Cu
Dirac Cu
7 5
VALENCE
1 0 2.0
2 0 2.0
2 1 6.0
3 0 2.0
3 1 6.0
3 2 10.0
4 0 1.0
SubEnd
BasisFunctions
3 2 1.65
4 0 1.0
4 1 2.0
SubEnd
FitFunctions
1 0 44.50
2 0 43.48
3 0 38.92
4 0 33.87
4 0 23.32
5 0 20.07
5 0 14.33
5 0 10.22
6 0 8.77
6 0 6.43
6 0 4.72
7 0 4.04
7 0 3.03
7 0 2.27
2 1 34.50
3 1 25.75
4 1 19.17
5 1 14.36
5 1 8.97
6 1 6.78
6 1 4.40
3 2 29.15
4 2 17.85
5 2 11.23
5 2 5.94
6 2 3.83
6 2 2.13
4 3 19.15
4 3 8.05
5 3 4.37
5 3 2.00
5 4 13.80
5 4 7.25
5 4 3.81
5 4 2.00
SubEnd
End
EndInput
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