Non self-consistent calculations: Band structures and Density Of States

Prev: LabQSM#Lecture 1: Basic DFT calculations and Convergences Next: [[]]

Non self-consistent calculations: Intro

Once the charge density has been obtained in a scf run, more calculations can be performed at fixed density (non-scf). Among these:

• calculations of Kohn-Sham energies and orbitals on any given set of k-points (i.e. without specific aim of represent a reasonable sampling of the BZ);
• calculations as above, also increasing the number of computed (= diagonalized) bands (incl the calculation of empty Kohn-Sham states);
• Importantly, nscf calculations are typically done to plot KS bands or compute the DOS,
• but also as a preliminary step to other calculations (e.g. uniform k-point samplings and large amounts of empty states are using in GW and other many-body perturbation theory algorithms implemented with sum-over-states techniques)

In the Quantum ESPRESSO input file one has to set:

   calculation="nscf"     # kpts sampling BZ

or

   calculation="bands"   # kpts along lines

K-points (and number of bands if relevant) need to be specified