Density of states calculation gives me density of states equal to 0?

exciting
1

Hello all,
Below is my input.xml file. I am trying to calculate the density of states for lithium and when I perform the exciting_smp calculation, I get values of 0. Since this should not be possible for lithium, what’s wrong with my input file? I would appreciate a prompt answer, I’m kind of desperate since I need this data for a paper I’m writing. Thanks.

<input>
<title>Lithium</title>
<structure speciespath="/root/exciting/species">
<crystal scale="6.6329">
<basevect>0.0 0.5 0.5</basevect>
<basevect>0.5 0.0 0.5</basevect>
<basevect>0.5 0.5 0.0</basevect>
</crystal>
<species speciesfile="Li.xml" rmt="1.6">
<atom coord="0.00 0.00 0.00"/>
<atom coord="0.5 0.5 0.5"/>
</species>
</structure>
<groundstate ngridk="8 8 8" outputlevel="normal" xctype="GGA_PBE_SOL"> </groundstate>
<properties>
<dos nsmdos="2" nwdos="100000" winddos="-0.3 40" inttype="tetra"> </dos>
</properties>
<xs xstype="TDDFT" ngridk="8 8 8" vkloff="0 0 0" nempty="5" gqmax="3.0" broad="0.04" tevout="true">
<energywindow intv="0.0 40.0" points="10000"/>
<tddft fxctype="ALDA" intraband="true"/>
<qpointset>
<qpoint> 0.0 0.0 0.00 </qpoint>
<qpoint> 0.0 0.0 0.1 </qpoint>
<qpoint> 0.0 0.0 0.20 </qpoint>
<qpoint> 0.0 0.0 0.3 </qpoint>
<qpoint> 0.0 0.0 0.40 </qpoint>
<qpoint> 0.0 0.0 0.5 </qpoint>
<qpoint> 0.0 0.0 0.60 </qpoint>
<qpoint> 0.0 0.0 0.7 </qpoint>
<qpoint> 0.0 0.0 0.80 </qpoint>
<qpoint> 0.0 0.0 0.9 </qpoint>
<qpoint> 0.0 0.0 1 </qpoint>
</qpointset>
</xs>
</input>
2

Hi Angela,

If I use a stripped-down input, where I’ve used less k-points for speed, and removed the TDDFT calc:

<input>
  <title>Lithium</title>
  <structure speciespath=".">
  <crystal scale="6.6329">
    <basevect>0.0 0.5 0.5</basevect>
    <basevect>0.5 0.0 0.5</basevect>
    <basevect>0.5 0.5 0.0</basevect>
  </crystal>
<species speciesfile="Li.xml" rmt="1.6">
<atom coord="0.00 0.00 0.00"/>
<atom coord="0.5 0.5 0.5"/>
</species>
</structure>
<groundstate ngridk="2 2 2" outputlevel="normal" xctype="GGA_PBE_SOL"> </groundstate>
<properties>
  <dos nsmdos="2" nwdos="100000" winddos="-0.3 40" inttype="tetra"> </dos>
</properties>
</input>

I have no problem running with serial or smp exciting. Although interesting mpi_smp hangs… I guess there’s some erroneous blocking MPI call.

There is data in the dos file, but I note that the cell vectors (basevect) should be in Bohr by default (see Structure - exciting). If I compare to the materials project, FCC Lithium primitive cell, I think you’ve used Angstrom instead. Please check this.

Otherwise, to plot your DOS data, you can use tools/exciting_tools (pip install it)

import numpy as np
import matplotlib.pyplot as plt

from excitingtools.exciting_dict_parsers.properties_parser import parse_dos

dos_dict = parse_dos('dos.xml')
n_points = 100000
dos = np.empty(shape=(n_points, 2))

for i in range(0, n_points):
    #unnecessary nesting structure to dict
    point_value = dos_dict['totaldos']['diagram']['point'][str(i+1)]
    dos[i, :] = np.array([point_value['e'], point_value['dos']])

fig, ax = plt.subplots()
ax.plot(dos[:, 0], dos[:, 1])
# Reduce x range, for erroneous-looking result
ax.set_xlim([0, 2])
plt.show()

I recommend doing the TDDFT calc as a separate input, and use the mpi_smp binary for this, else you don’t get k-point parallelisation.

Cheers,
Alex

3

Hi Alex, thanks so much for your input and on my other post as well.

Looking back on my input file, the numbers we were trying to use were for BCC Lithium and I used the incorrect cell vectors. That could have been the issue; I also got data using smp exciting, it was just that a lot of the data gave me 0 where there should not have been any zeroes. I may try another calculation using these BCC base vectors instead:

  <crystal scale="6.6329">
    <basevect>0.5 0.5 0.5</basevect>
    <basevect>-0.5 0.5 0.5</basevect>
    <basevect>-0.5 -0.5 0.5</basevect>
  </crystal>

If that poses any issues, I’ll be sure to make another post here.
Best regards,
Angela