# [DFTB-Plus-User] DOS Fermi Energy problem

Ezgi Erdogan ezgierdo at gmail.com
Thu Aug 20 15:03:26 CEST 2009

```Dear users,
I would like to ask you the density of states (DOS) graphics. I have trouble
around fermi level.

1- Proper Density and Unitcell Geometry
a) dftb_in_dos.hsd input file is:
///////////////////////////////////////////////
Geometry = GenFormat {
<<<"dftb_in.geometry.gen"
}

Hamiltonian = DFTB {
SCC = No
SCCTolerance = 1e-5
MaxAngularMomentum = {
C = "p"
H = "s"
}
SlaterKosterFiles = {
C-C = ""
C-H = ""
H-C = ""
H-H = ""

}
PolynomialRepulsive = SetForAll{No}

KPointsAndWeights = SupercellFolding {
8   0     0
0   1     0
0   0     1
0.5 0.0  0.0
}
}

b) dftb_in_dos.geometry.gen
///////////////////////////////////////////
For Density of State calculation we have to shift our geometry to Unitcell.
28  S
C  H
1 2      0.98140000      1.04655000      0.00000000
2 1      1.54350100      1.97980000      0.00000000
3 1      0.85434800      3.22200000      0.00000000
4 1      1.52784100      4.44910000      0.00000000
5 1      0.83841700      5.70995000      0.00000000
6 1      1.52558700      6.93745000      0.00000000
7 1      0.85861600      8.16790000      0.00000000
8 1      1.55011300      9.44240000      0.00000000
9 1      0.88311300     10.67285000      0.00000000
10 1      1.56219600     11.92150000      0.00000000
11 1      0.86961700     13.18065000      0.00000000
12 1      1.52639800     14.42235000      0.00000000
13 1      0.76925600     15.62445000      0.00000000
14 2      1.44626500     16.47830000      0.00000000
15 2      3.49406700      1.00195000      0.00000000
16 1      2.96557000      1.95460000      0.00000000
17 1      3.69848600      3.17155000      0.00000000
18 1      3.00933300      4.41370000      0.00000000
19 1      3.70284500      5.69035000      0.00000000
20 1      3.02619500      6.93325000      0.00000000
21 1      3.69503000      8.16930000      0.00000000
22 1      3.00756000      9.44100000      0.00000000
23 1      3.67642400     10.67705000      0.00000000
24 1      2.99974500     11.91995000      0.00000000
25 1      3.68177400     13.20275000      0.00000000
26 1      3.00338200     14.40000000      0.00000000
27 1      3.60368600     15.68735000      0.00000000
28 2      2.82484200     16.44975000      0.00000000
0.00000000      0.00000000      0.00000000
5.009544167      0.00000000      0.00000000
0.00000000     50.00000000      0.00000000
0.00000000      0.00000000     50.00000000

2- Run this input and geometry.

Look for Fermi Energy Level.
Fermi energy:                    -0.1837716172 H       -5.000680 eV
Band energy:                    -43.6825057076 H    -1188.661459 eV
TS:                               0.0000000000 H        0.000000 eV
Band free energy (E-TS):        -43.6825057076 H    -1188.661459 eV
Extrapolated E(0K):             -43.6825057076 H    -1188.661459 eV

Energy H0:                        0.0000000000 H        0.000000 eV
Total Electronic energy:        -43.6825057076 H    -1188.661459 eV
Repulsive energy:                 1.4070475536 H       38.287712 eV
Total energy:                   -42.2754581540 H    -1150.373747 eV
Total Mermin free energy:       -42.2754581540 H    -1150.373747 eV

Calculation with static geometry

Non-SCC calculation

2- For proper dos.dat plotting we have to use 2 scripts :

band2dat and dosplot.in

a)  band2dat -N dftb_in_dos.band.out band.dat
b)   for dosplot in:

[gauss]
coefficient = 0.2
exponent = 20.0
[data]
nr_kpoints = 50   #change this which k point you want to calculate
kweights =  1.000000

eigenvalues = << dftb_in_dos.dat
eigval_order = k_major

dosplot dosplot.in > dos.dat      if you run from your folder "bin"

3-  and to plot:
xmgrace dos.dat

Now here is my question is coming. In this geometry there should be confused
Fermi Energy Level or I am calculating in wrong way? So which Fermi Energy
Level in this DOS graphics should be done. From detailed.out file we can
say:  Fermi energy: -0.1837716172 H       -5.000680 eV. To shift +Efermi
Level or -Efermi Level or just draw this plot between -4  to 4 or what could
be other solution? For my further calculation I have to get proper Fermi
Energy Level and DOS graphs.

Thank you for support

Ezgi
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