Density Of States

To calculate the density of States different switches and modes are present in the inp-file:

  • Most important, dos hast to bet set to .true.

    strho=F,film=F,dos=T

  • The energy window, where the DOS is calculates is specified at the end of the inp-file:

    emin_dos= -0.50000,emax_dos= 0.50000,sig_dos= 0.00050

Note, that this is in Hartree units and not referred to some Fermi-level. The DOS is broadened by a Gaussian with the width sig_dos (also in htr.).

  • A little bit nicer DOS' can be produced with the tetrahedron (3D) or triangular (2D) method. For films this is used whenever the k-point set allows it (corner points are included). For bulk, you have to create a k-point set with tria=T in the inp-file.

  • Finally, there is the switch ndir in the first line of the inp-file. it is used trigger the following:

    • Producing raw-data for a DOS in the a dosinp-file
    • Integrated DOS programm gives DOS.x files
    • Orbital decomposition of the DOS

Note that you have to delete the fl7para and kpts files if you want to calculate the DOS.

Producing Raw-data For A DOS

  1. Setting dos=t and ndir=0 in the inp-file switches into the DOS-mode of FLEUR. In this mode a dosinp-file is created which contains the eigenvalues and thier relative weights for all kpts.
  2. Similarly, one obtains a vacDOS file containing the LDOS in the vacuum by setting vacdos=t.
  3. By setting dos=t and ndir>0 one obtains a dosinp-file with additional symmetry-information which is used for band-structure plotting

IntegratedDOSProgramm

total & partial DOS

By setting dos=t and ndir<0 the integrated DOS program is used. Three additional parameters in the inp file have to be specified in this case. The two energies emin_dos and emax_dos specify the energy-range in which the DOS is evaluated. The parameter sig_dos specifies the broadening, as shown below (where the last few lines of the input file are given. 

vacdos=T,layers= 1,integ=F,star=T,nstars= 2
 50
 iplot=F,score=F,plpot=F
 0  0.000000  0.000000,nnne=  0,pallst=F
 xa=   2.00000,thetad= 300.00000,epsdisp=   0.00010,epsforce=   0.00010
 relax 000
 emin_dos=    -1.000,emax_dos=   0.00000,sig_dos=   0.00050

Three different negative values for ndir are implemented at the moment:

  • ndir=-1: In this mode FLEUR calculates the DOS-output and stops without creating a new charge density. This is analogous to the old DOS-mode
  • ndir=-2: In this mode FLEUR calculates the DOS-output and creates a new charge density afterwards. This is done only if it=itmax, so that one can use this setting to create a DOS during self-consistency iterations.
  • ndir=-3: In this mode the Orbital decomposition of the DOS is calculated

For information about the output see the documentation of the DOS.x file.

vacuum DOS

If one wishes to calculate the DOS in selected parts of the vacuum region, the parameter vacdos=T has to be set. In combination with dos=T and ndir=-1, this will generally produce a file VACDOS.[1,2] which has a format as describec in the documentation of the DOS.x file.

This is done by integrating over the 2-D unit cell and in z-direction one can either integrate (integ=T) up several layers (defined by layers= in the inp-file), or choose planes, where the DOS is evaluated.

  • If integ=F, the line below should provide as many integer numbers, as the number of layers that has been defined. The z-position of a layer with number N is given by: 
           dvac    N
       z = ---- + --  (a.u.)
             2    10

i.e. in the sample inp the layer # 50 is at 11 a.u. or about 3.07 Angstroem above the topmost Cu atom. The format is (in FORTRAN) (20(i3,1x)), i.e. a maximum of 20 planes can be defined. By default, the largest number (N) that can be entered is 250.

Notice, that there is a parameter layerd in the fl7para file. Typically, this should be increased to the number of layers.

  • If integration is choosen, then the next line in the inp-file defines pairs of z_low and z_up for integration. Again the pairsare given in integers as described above. The format here is (10(2(i3,1x),1x)), i.e. up to 10 regions can be integrated.

  • If you are interested in the lateral modulation of the local DOS in the vacuum, you can plot the (symmetrized) Fourier-components of the DOS by setting star=T, as long as you are within 10 a.u. from the vacuum matching plane (i.e. dvac/2). The number of Fourier-components you want so see in your VACDOS.[1,2] file is defined by nstars=.

  • Many more features are built in, but usually the ones described above should suffice. In any case they are mainly tested within collinear calculations (without SOC), so be careful.

Orbital Decomposition Of The DOS

In cases it might be useful to obtain also the orbital decomposed density of states of a certain atom. To get a DOS.x file with this information, you have to specify 

dos=T

and 

ndir=-3

in the inp file. Additionally, a file named orbcomp has to be present in the working directory, where the number of an atom (counted in the order as it appears in the inp file) is specified. Then, the DOS-file contains information about the selected atom (not atom-type!) in the following form (the energy is in eV): 

energy  total-DOS                     selected atom-type
                   s   p   p   p   d    d    d    d      d   f   f   f   f   ...
                       x   y   z   xy   yz   zx   x²-y²  z²  x³  y³  z³  x²y

(Note: you have to provide k-points in the whole Brillouin-zone to get a correct DOS here! Proper symmetrization will be implemented in future releases.) The other f-components can be found in the file ek_orco.[1,2], where also the orbital composition is given for each k-point. To get this file, 

cdinf=T

should be set in the inp-file.

rotated coordinate frames

Since the decomposition in spherical harmonics is per default performed in the global coordinate frame, it can be sometimes useful to have a tool to perform the decomposition in a rotated coordinate frame. For this, another file orbcomprot has to be specified that contains three lines, specifying the Euler-angles \alpha, \beta and \gamma for the rotation.

layer resolved DOS

If a zero is specified in the orbcomp file, or no such file has been provided, then the DOS.x files will contain the information about the layer resolved DOS. This is especially meaningful for a film-calculation, where the film can be divided into layers; the boundaries of the layers are defined as (x,y)-planes that intersects halfway between two neighbouring atoms of different height in the film. The results are listed in the following form: 

energy  total-DOS   layer            interstitial         muffin-tin 
                                contribution to layer
                     1, 2, ... n      1, 2, ... n          1, 2, ... n