Hartree Fock

Prerequisites

• Complete the Generating the Yambo databases tutorial
• SAVE folder for bulk hBN.
• yambo executable
• Run Initialization

The exchange part contribution of the self-energy for a generic state (nk) in reciprocal space reads:

It is important to note that in this way we are adding the HF contribution in a perturbative way to previously calculated DFT energies:

and hence they will differ from a standard self-consistent HF calculation.

Let's start by building up the input file for an HF calculation by typing:

$ yambo -x -V all -F hf.in

Looking inside the input file you will find:

EXXRLvcs = 1491        RL    # [XX] Exchange RL components
%QPkrange                    # [GW] QP generalized Kpoint/Band indices
  1| 14|  1|100|
%

The variable EXXRLvcs governs the number of G vector to be summed in the expression of the exchange self-energy reported above. The QPkrange name list it is a generalized index needed to select the first and last kpoints and bands we want to calculate the QP correction. Let's start by editing the hf.in file by considering the last occupied and first empty bands in order to calculate the direct gap, and run calculations to converge the expression above. In the expression of the Exchange Self Energy, we have a summation over bands, an integral over the Brillouin Zone and a Sum over bands. Sum over bands

check convergence of the G vectors in the summation in the Σx expression. So we change the QPkrange variable in:

%QPkrange                    # [GW] QP generalized Kpoint/Band indices
   14| 14|  8| 9|
%

and

EXXRLvcs= 10 Ry

and run yambo:

$ yambo -F hf.in -J 3D

Links

• Back to tutorials menu
• Back to How to obtain the quasi-particle band structure of a bulk material: h-BN