Fermi surface

The Fermi surface is visualized by XCrySDen [105] and FermiSurfer [143,144]. When you perform calculations of the density of states by the following keywords:

  Dos.fileout                  on        # on|off, default=off
  Dos.Erange              -20.0  20.0    # default = -20 20 
  Dos.Kgrid                 61 61 61     # default = Kgrid1 Kgrid2 Kgrid3
  FermiSurfer.fileout         on         # default = off, on/off

you will obtain a file 'System.Name.FermiSurf0.bxsf' which is readable by XCrySDen [105] and a file 'System.Name.FermiSurf_s0_aA.frmsf' which is readable by FermiSurfer [143,144], where 'System.Name' is 'System.Name', and A is the serial number of atoms. To obtain the files readable by FermiSurfer, you need to switch on the keyword 'FermiSurfer.fileout'. As well as 'Dos.Fileout', 'DosGauss.fileout' can also be used for the purpose, while the files readable by FermiSurfer are not generated in the case of 'DosGauss.fileout'. In case of spin-polarized calculations, for XCrySDen two files 'System.Name.FermiSurf0.bxsf' and 'System.Name.FermiSurf1.bxsf' are generated for spin-up and spin-down states, respectively, and for FermiSurfer two files 'System.Name.FermiSurf_s0_aA.frmsf' and 'System.Name.FermiSurf_s1_aA.frmsf' are generated for spin-up and spin-down states, respectively. The data file for FermiSurfer can be used to display the color plot of the contribution from each atoms.

Figure 89: Fermi surfaces of the fcc Ca bulk visualized by XCrySDen [105] in (a) and (b). Since two sorts of bands intersect with the Fermi energy (chemical potential), two Fermi surfaces are shown in (a) and (b). (c) The color plot of the Fermi velocity of the material: the plot is visualized by using FermiSurfer [143,144]. The input file used for the calculation is 'Cafcc_FS.dat' in the directory 'work'.

For example, if we plot the character of atomic orbitals of the atom 1, we read 'System.Name.FermiSurf_s0_a1.frmsf'. In case of non-collinear calculations, a file 'System.Name.FermiSurf.bxs' and 'System.Name.FermiSurf_aA.frmsf' are generated. It is noted that a large number of k-points should be used in order to obtain a smooth Fermi surface. As an example, Fermi surfaces of the fcc Ca bulk are shown in Fig. 89. The input file used for the calculation is available as 'Cafcc_FS.dat' in the directory 'work'.