UV/Vis spectrum of Ir(ppy)3

In this tutorial we will use time-dependent DFTB to calculate the UV/Vis absorption spectrum of the Iridium complex Ir(ppy)3.

Start ADFinput
Obtain a Ir(ppy)3 molecule by pasting the following coordinates into ADFinput:
Ir    0.012398    0.011138   -0.034888
N    -0.039454    0.033020    2.182572
C     1.196760   -0.025409    2.759734
C     1.312058    0.049492    4.160403
H     2.297136    0.010793    4.623158
C     0.176907    0.180049    4.949521
H     0.267945    0.241793    6.035562
C    -1.080728    0.227837    4.337521
H    -1.998559    0.321169    4.918229
C    -1.136029    0.147902    2.951293
H    -2.086922    0.175812    2.417126
C     2.320171   -0.152466    1.829294
C     2.023265   -0.155989    0.436568
C     3.102011   -0.288673   -0.454369
H     2.909074   -0.300226   -1.528367
C     4.415258   -0.411210    0.002305
C     4.695599   -0.406624    1.375984
H     5.722404   -0.504771    1.732389
C     3.649435   -0.277487    2.282572
H     3.871783   -0.280893    3.351436
H     5.231463   -0.511562   -0.717544
C     0.348035    0.181591   -2.073796
C     0.477555    1.514919   -2.556751
C     0.724684    1.764358   -3.922454
H     0.829885    2.787826   -4.287727
C     0.844594    0.712499   -4.823508
H     1.037805    0.912270   -5.878913
C     0.719659   -0.604432   -4.359020
H     0.813485   -1.438052   -5.059452
C     0.474019   -0.859703   -3.009006
H     0.385255   -1.893716   -2.671738
C     0.365837    2.600714   -1.582092
N     0.167789    2.211524   -0.287922
C     0.070484    3.136313    0.682683
H    -0.072051    2.747901    1.692346
C     0.145763    4.501897    0.436809
C     0.336880    4.923011   -0.884173
H     0.401581    5.985888   -1.124354
C     0.445887    3.971689   -1.889620
H     0.597414    4.283773   -2.922014
H     0.063205    5.212485    1.259290
N    -2.184281   -0.109350   -0.312568
C    -2.661123   -1.388612   -0.350406
C    -4.046619   -1.609170   -0.458307
H    -4.429551   -2.628420   -0.482142
C    -4.923390   -0.534729   -0.529917
H    -5.997987   -0.707636   -0.612774
C    -4.412321    0.767839   -0.500666
H    -5.061792    1.641013   -0.565173
C    -3.036095    0.927439   -0.392594
H    -2.577985    1.917423   -0.370095
C    -1.646438   -2.441110   -0.271132
C    -0.290616   -2.036409   -0.112573
C     0.684523   -3.046718   -0.059045
H     1.733837   -2.770376    0.056220
C     0.343229   -4.396378   -0.157833
C    -0.995273   -4.783541   -0.314549
H    -1.261180   -5.838892   -0.394860
C    -1.983096   -3.806784   -0.368630
H    -3.023159   -4.112311   -0.498560
H     1.126462   -5.157297   -0.113713
Select the DFTB panel: panel bar ADF → DFTB
Choose SinglePoint as the Task to perform

TD-DFTB is based on the SCC extension to DFTB and is therefore best used with the SCC-DFTB model. It is also incompatible with fractional occupation numbers, so we switch to the Aufbau occupation scheme.

Set the Model to SCC-DFTB
Select the Aufbau Occupation scheme

We need to select a parameter set that includes Iridium.

Change the parameter directory to QUASINANO2013.1

We want to obtain the absorption spectrum up to 6 eV, so we allow for some safety margin and calculate all singlet-singlet excitations up to 6.8 eV which is 0.25 Hartree. The “Number of excitations” field acts an upper limit for the calculated number of excitations if the “Excitations up to” field is used. We do not need an upper limit for this tutorial, so we set it to something large.

Use the panel bar Properties → Excitations (UV/Vis) to go to the TD-DFTB configuration
Select SingletOnly as the Type of excitations to calculate
Change the Number of excitations to calculate to 10000
Calculate Excitations up to 0.25 Hartree
../_images/irppy3settings.png

We are now ready to run the calculation. It should only take a few seconds.

Save your input using File → Save as ...
Run the calculation with File → Run
Wait for the calculation to finish

We can now use ADFspectra to have a look at the results.

Select SCM → Spectra
../_images/irppy3spectrum.png