CASINO manual - Theory of Condensed Matter

Potential
Repeat distance (au)
3.d0
Number of Gaussians
2
Coefficients and exponents
1.d0 6.d0
1.d0 2.d0
‘NUMERICAL PERIODIC’ Periodic numerical representation on a grid.
Potential
Repeat distance
3.d0 au
Number of grid points
2000
Grid point ; function value
0.01 2.345
0.02 2.456
...
2.d0 0.000
3. The Type of orbitals may take the following value (more to be added on request/need):
‘FOURIER’ One-dimensional Fourier series in the z-direction, plane waves in the XY plane.
Period L (au)
20.0
Symmetry (even/odd/none)
NONE
Number of terms n (excluding a0)
15
Number of bands
2
START BAND 1
Occupation
13
Fourier coefficients (a0 ; a_i,b_i {i=1,n}. Omit a/b if symm ODD/EVEN)
0.08197602811796 [a0]
0.00000000000000 0.00000000011629 [a1 b1]
-0.07488206414295 -0.00000000158436 [a2 b2]
... [13 more rows, according to the value of n=15 given above]
END BAND 1
START BAND 2
Occupation
11
Fourier coefficients (a0 ; a_i,b_i {i=1,n}. Omit a/b if symm ODD/EVEN)
...
END BAND 2
4. The file version is an integer, which is always increased if the specification for this file changes.
5. Where more than one set is given, the potentials defined in the different sets are added to give
the final potential at a particular point.
6. The Direction parameter gives the direction along which a particular potential varies. This
may be along one of the three lattice vectors (periodic systems), along the x, y or z axes, or
along a custom direction given in input. If the Direction parameter is ‘ISOTROPIC’ then the
potential varies radially as a function of distance from the given point.
7. In the case of the Fourier expansion, complex coefficients need to satisfy c G = c ∗ −G if the
potential is to be real. This will be checked for. With pure real coefficients the option exists of
omitting the imaginary part of the Fourier coefficients section in order to save disk space.
8. For periodic types the external potential will be checked for being commensurate with the
underlying lattice.
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