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Background

This lesson focuses on the calculation of density of states (DOSes) and of electronic band structures within the Kohn-Sham (KS) formalism.

In contrast to the total energy and its derivatives, the energies of the KS levels have no physical meaning, except for the highest occupied state that actually would be the first ionization energy if the DFT XC functional would be exact. So why do we use the KS formalism to calculate electron DOSes and band structures?

As a matter of fact, the KS energy spectrum is usually in qualitative agreement with experiments (let's ignore correlated systems). Standard KS band structures with LDA or GGA are relatively cheap and KS calculations allow us to make reasonable predictions and to study trends. In lesson_g0w0.py, we discuss a more accurate and expensive approach for the calculation of band structures and band gaps based on many-body perturbation theory.

The related abinit variables

    •   kptopt (negative values if band structures are wanted)

    •   kptbounds (the boundaries of the k-path)

    •   ndivsm (number of points used to sample the smallest segment of the k-path)

The full description, directly from the abinit documentation, is available via the following function:

        abidoc.py man inputvariable

This will print the official abinit description of this inputvariable.

The course of this lesson