Fermi Surfaces with Siesta

Siesta is not really optimal for systems with small, highly-symmetric, unit cells, but it is still possible to use it to generate the copper Fermi surface shown in the other examples. A minimum c2x version of 2.34a is required below.

copper.fdf

LatticeConstant  1.0 Ang
%block LatticeVectors
-1.766923 0.000000 1.766923
0.000000 1.766923 1.766923
-1.766923 1.766923 0.000000
%endblock LatticeVectors

NumberOfAtoms    1
NumberOfSpecies  1
%block ChemicalSpeciesLabel
1  29   Cu
%endblock ChemicalSpeciesLabel

AtomicCoordinatesFormat Fractional
%block AtomicCoordinatesAndAtomicSpecies
 0.000000 0.000000 0.000000 1
%endblock AtomicCoordinatesAndAtomicSpecies

%block kgrid_Monkhorst_Pack
9 0 0 0.000000
0 9 0 0.000000
0 0 9 0.000000
%endblock kgrid_Monkhorst_Pack

The above suffices for the self-consistent part of the calculation, and unfortunately Siesta does not reduce the kpoint grid by anything more than inversion symmetry, so the 9x9x9 grid results in rather a lot of kpoints.

For the finer grid used for the non self-consistent calculation, again Siesta does not support symmetry, but it is possible to ask it to calculate on a pre-symmetrised list of kpoints. This list can be generated with c2x, so, before running the above calculation, one can type:

$ c2x -M=45,45,45 --fdf_bp copper.fdf >> copper.fdf

This will append to copper.fdf a section starting

# generated by c2x as a 45x45x45 grid, 2300 points after symmetrisation
BandLinesScale ReciprocalLatticeVectors
%block BandPoints
0.000000000 0.000000000 0.000000000
0.000000000 0.000000000 0.022222222

The required pseudopotential, Cu.psf, can be obtained from Cornell's Pseudopotential Virtual Vault as Cu.psf.

$ curl -O http://nninc.cnf.cornell.edu/psp_files/Cu.psf

Then Siesta can then be run as usual

$ siesta < copper.fdf > out.log

and c2x can then process the .bands file (from 2.34a it automatically detects whether a .bands file is in Castep or Siesta format):

$ c2x --bxsf siesta.bands siesta.bxsf
$ xcrysden --bxsf siesta.bxsf &

Cu Fermi surface