## What is SCF calculation in quantum espresso?

0.1 Single-point (fixed-ion) SCF calculation. For LSDA spin-polarized calculations (that is: with a fixed quantization axis for magnetization), set nspin=2. Note that the number of k-points will be internally doubled (one set of k-points for spin-up, one set for spin-down).

**How do you choose Pseudopotential in Quantum Espresso?**

The best pseudopotential depends on the problem you want to solve and if you want to add spin-orbit effects or not. As a general rule PAW pseudos tend to be the best, but it depends on what you want to study.

### How do you calculate SCF?

SCF Calculation for Two Electron Atoms and Ions

- Supply nuclear charge and an input value for β: Z=2β=2α=Z.
- Define orbital energies of the electrons in terms of the variational parameters: ε1sα(α, β)=α22−Zα+αβ(α2+3αβ+β2)(α+β)3ε1sβ(α, β)=β22−Zβ+αβ(α2+3αβ+β2)(α+β)3.

**What is the difference between PBE and PBEsol?**

A simple modification of PBE is the PBEsol functional, which differs from PBE only in two parameters, and is designed to improve upon PBE for equilibrium properties of bulk solids and their surfaces. The main difference between them is that they are based upon different selections of exact constraints to satisfy.

## What are PAW potentials?

Projector augmented wave (PAW) potentials are available for all elements in the periodic table from the VASP Portal. These are pseudopotentials for the PAW method and are stored in POTCAR files. The distributed PAW potentials have been generated by G.

**How do you optimize structures in Quantum ESPRESSO?**

There are two types of structural optimization calculations in Quantum espresso: (1) relax: where only the atomic positions are allowed to vary, and (2) vc-relax: which allows to vary both the atomic positions and lattice constants. Lattice constant = 0.364556379 * 14 / 0.5 = 10.2076 Bohr.

### How do you install Quantum ESPRESSO?

1. Day 1 (installation)

- Install Quantum Espresso.
- (a) First of all, install the following basic software by typing.
- $sudo apt-get install build-essential fftw3-dev gfortran.
- (b) Then, install software to be used for graphical analysis.
- $sudo apt-get install xcrysden.
- $sudo apt-get install gnuplot.

**How do I calculate the band structure?**

The bandstructure calculation requires four major steps: a relax calculation, a dense nscf (or scf if you are adventurous) k-point calculation, a bands calculation, finally followed post-processing with bands.x and plotband.x if you desire.

## How to get band structure from QE hybrid functional calculation?

Run your QE hybrid functional calculation (obviously use the correct mpi commands for your system when running in parallel): $ pw.x -inp silicon.in > silicon.out Doing the above I got this band structure.

**Does the density of the Q mesh affect the band-structure calculation?**

The bottom-line here is, the density of the ‘q’ mesh will affect the precision of the band-structure calculation since the basis is mathematical (for the Wannier method, this is not the case). ii) Install BoltzTrap2. Rename the SCF input and output files as prefix.nscf.in and prefix.nscf.out .

### Will this tutorial work for my Quantum ESPRESSO version?

This tutorial should also work for a range of Quantum Espresso (QE) versions as well, however they changed the way post-processing takes input files around 5.x so you may get some errors if you use them verbatim. If you do experience errors, feel free to email me if you cannot find proper documentation online for your QE version.