YAMBO is a code for Many-Body calculations in solid state and molecular physics to accurately determine excited states. YAMBO relies on the Kohn-Sham wavefunctions generated by DFT codes such as Quantum Espresso (QE). In this set of tutorials, you will first learn how to configure YAMBO with QE on JHU-MARCC and then you can practice running a range of calculations covering various topics. Tutorials include ground state calculation, file conversion, quasiparticle GW band structure calculation, and the calculation of optical absorption spectra using the Bethe-Salpeter equation (BSE).
The primary reference for YAMBO code is the article:
Yambo: an ab initio tool for excited state calculations, Andrea Marini, Conor Hogan, Myrta Grüning, Daniele Varsano, Comp. Phys. Comm. 180, 1392 (2009).
- How to Install (pdf download)
- Ground State Calculation as Starting Point for YAMBO (pdf download)
The initial step is to generate the ground state wavefunction for the proposed system using Quantum Espresso. In this tutorial we are going to use single layer MoS2 as an example material for our QE ground state calculation. We discuss the specific input parameters used for both self-consistency (SCF) and non-self-consistency (NSCF) runs to obtain the ground state wavefunction, which we will then use for YAMBO calculations. Please go to the Quantum Espresso Tutorial if you need further information about QE.
- File Conversion from QE to YAMBO (pdf download)
In this tutorial we are going to learn how to convert QE-generated wavefunctions into YAMBO-readable format. These wavefunctions will be the basis for the calculation of excited states in the following step.
- GW Band Structure (pdf download)
DFT methods usually underestimate the band gap. In this tutorial we are going to learn how to calculate the quasiparticle correction to the band gap using the GW approximation implemented in YAMBO. We are going to use the command line to generate the input file for the GW calculation. We are also going to discuss the input parameters that require convergence tests during the GW calculation.
- Postprocessing of the Quasiparticle Energies to Obtain the GW Band Structure (pdf download)
Once the GW calculation is completed, we are going to use the yambo post-processor ypp, along with a set of commands, to plot the GW band structure.
- Calculation of Optical Properties with YAMBO (pdf download)
In this tutorial we are going to calculate the optical absorption spectrum using the GW-BSE method implemented in YAMBO. We are going to calculate the absorption spectrum including the quasiparticle correction for single layer MoS2. Before starting this tutorial, you must first complete the GW tutorial since this calculation depends on previously calculated corrected quasiparticle energies.