Projected Density of States
In this tutorial, we will using Optados to calculate the electronic density of states of 2 atoms of crystalline silicon projected onto LCAO basis states. It may be helpful to have gone through the previous tutorial on calculating the DoS.
We will use the cell file
Si.cell
%BLOCK LATTICE_CART
2.73 2.73 0.00
2.73 0.00 2.73
0.00 2.73 2.73
%ENDBLOCK LATTICE_CART
%BLOCK POSITIONS_FRAC
Si 0.0 0.0 0.0
Si 0.25 0.25 0.25
%ENDBLOCK POSITIONS_FRAC
SYMMETRY_GENERATE
KPOINTS_MP_GRID 10 10 10
SPECTRAL_KPOINTS_MP_GRID 12 12 12
and the param file
Si.param
TASK : SPECTRAL
%BLOCK devel_code
spectral: check_output: true :endspectral
%ENDBLOCK devel_code
SPECTRAL_TASK : DOS
PDOS_CALCULATE_WEIGHTS : TRUE
CUT_OFF_ENERGY : 200
IPRINT : 1
Run castep. Then, run Optados with the Optados input file
Si.odi
TASK : pdos
PDOS : angular
EFERMI : optados
DOS_SPACING : 0.1
BROADENING : adaptive # Default
ADAPTIVE_SMEARING : 0.4 # Default
FIXED_SMEARING : 0.3 # Default
SET_EFERMI_ZERO : true # Default
DOS_PER_VOLUME : false # Default
NUMERICAL_INTDOS : false # Default
FINITE_BIN_CORRECTION : true # Default
Note the line TASK : pdos - this is what allows us to calculate the PDoS. We have chosen to decompose the DOS into angular momentum channels with the line 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.
The output can be found in Si2.pdos.dat - it contains the header below to tell us what each column represnts.
################################################################
#
# 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 |
#+-------------------------------------------------------------+
This shows that there are four projectors described below - each one corresponding to a column in the actual data. The 1st contains the s-channels of both silicon atoms, the 2nd the p-channels etc. The values correspond to the sums of the values of both Si atoms.
You can change which projectors you will gain by changing the line PDOS : ANGULAR. Changing the value to SPECIES_ANG will give you only the first 2 projectors. SPECIES will yield the sum of all the orbitals and atoms. SITES will give you 1 projector of the sum of all orbitals of Si atom 1, and 1 of atom 2 (note that they're identical). You can also make custom projectors - write down the element, number and orbital in brackets, with columns separating adjacent projectors if you want multiple. For example, Si1(s):Si2(p) will give you 1 column of the PDoS of the s orbital on silicon atom 1, and a column of the p orbital on silicon atom 2.
Note
Using custom projectors won't save the data in Si.pdos.dat, but a file named based on the projectors chosen - in the example above, it'd be saved in Si.pdos.proj-0001-0002.dat.
The output is easily plotted by using xmgrace on the dat file. To plot multiple bits of data, it is easiest to use a batch file - this is the plot of the s and p channels: We can run xmgrace -batch pdos_plot.bat on the batch file
pdos_plot.bat
to get the following output:
