Excited States

This exercise investigates the properties and usability of several materials in terms of applications in photovoltaics.

The exercise will teach you how to set up your material and investigate the most important parameters like the band gap and the absorption spectrum from first principles calculations. The first part shows how to calculate a converged band structure. In the second part you will learn to calculate the quasiparticle band gap. The third part involves learning how to calculate an absorption spectrum within the random phase approximation. Finally, you will calculate the absorption spectrum including excitonic effects and compare different materials in the fourth part.

Part 1: Setup of the structure and bandstructure calculations

The notebook es1.ipynb shows how to set up the material and how to calculate a converged band structure.

  • Set up the atomic structure and optimize its geometry

  • Calculate the band gap, band gap position, and band structure

  • Compare the performance of different exchange correlation functionals

Part 2: Quasiparticle bandgap

The notebook es2.ipynb teaches how to set up calculations to find the quasiparticle band gap using GW approximation.

  • Understanding the GW approximation.

  • First basic tests on the convergence of quasiparticle spectrum.

  • Write/submit batch jobs

Part 3: Absorption spectrum

The notebook es3.ipynb teaches how to set up calculations of the dielectric function to find the absorption spectrum.

  • Understanding the dielectric function

  • First basic tests on the convergence of absorption spectra in the random phase approximation

  • Write/submit batch jobs

Part 4: Excitonic effects and Discussion

In the last notebook es4.ipynb the results for different materials are plotted and discussed. Next the absorption spectra is calculated including the excitonic effects (Bethe-Salpeter formalism).

  • Understanding the excitonic effects and Bethe-Salpeter formalism.

  • Basic tests on convergence of the absorption spectra.

  • Write/submit batch jobs

Special care is taken of the convergence.