Tutorials

Projected Density of States

We assume the reader is familiar with the previous section on Density of States calculations and is now familiar with running optados.

Outline

This is a simple example of using optados for calculating electronic density of states of 2 atoms of crystalline silicon projected onto LCAO basis states.

Input Files

  • examples/Si2_PDOS/Si2.cell - The castep cell file containing information about the simulation cell.
  • examples/Si2_PDOS/Si2.param - The castep param file containing information about the parameters for the SCF and spectral calculations.
  • examples/Si2_PDOS/Si2.odi - The optados input file, containing the parameters necessary to run optados.

INSTRUCTIONS:

  • Examine the optados input file noting TASK : pdos. We choose to decompose the DOS into angular momentum channels PDOS : angular and as in the previous example we choose to recalculate the Fermi level using the calculated DOS, rather than use the Fermi level suggested by castep.
  • Execute optados.
  • The output can be found in Si2.pdos.dat.
################################################################
#
#                  O p t a D O S   o u t p u t   f i l e
#
#  Generated on 13 Feb 2012 at 10:15:10
################################################################
#+-------------------------------------------------------------+
#|                    Partial Density of States -- Projectors  |
#+-------------------------------------------------------------+
#| Projector:    1 contains:                                   |
#|           Atom            AngM Channel                      |
#|          Si   1                 s                           |
#|          Si   2                 s                           |
#+-------------------------------------------------------------+
#| Projector:    2 contains:                                   |
#|           Atom            AngM Channel                      |
#|          Si   1                 p                           |
#|          Si   2                 p                           |
#+-------------------------------------------------------------+
#| Projector:    3 contains:                                   |
#|           Atom            AngM Channel                      |
#|          Si   1                 d                           |
#|          Si   2                 d                           |
#+-------------------------------------------------------------+
#| Projector:    4 contains:                                   |
#|           Atom            AngM Channel                      |
#|          Si   1                 f                           |
#|          Si   2                 f                           |
#+-------------------------------------------------------------+

The header shows that there are four projectors described below. The first containing the s-channels of both silicon atoms, the second the p-channels etc.

  • The output is easily plotted using xmgrace:
  • Setting DOS_SPACING : 0.001 gives a high quality plot, as shown in Fig1


Fig1. Density of States of Silicon generated by adaptive broadening projected onto LCAO momentum states.}

Other projections to try are:

  • PDOS : Si1;Si2(s) -- Output the PDOS on Si atom 1 and the PDOS on the s-channel of Si atom 2. (Resulting in two projectors)
  • PDOS : sum:Si1-2(s) -- Output the sum of the s-channels on the two Si atoms. (Resulting in one projector)
  • PDOS : Si1(p) -- Output the p-channel on Si atom 1. (Resulting in one projector)