Accuracy and Efficiency¶

Given a Model Hamiltonian, the most important aspects determining the accuracy of a Band calculation are:

• Basis set

• K-Space

Also important, but to a lesser degree, are the following aspects:

• Numerical Integration (BeckeGrid)

• Density fitting (ZlmFit)

• Basis-set confinement (SoftConfinement)

• SCF convergence (Convergence)

• Hartree–Fock Resolution of the Identity (RIHartreeFock) (only for hybrid functionals)

• For Many-body-perturbation theory (MBPT) options (only for MBPT calculations)

The CPU time and memory requirements strongly depend on these options, as does the accuracy of the results.

General NumericalQuality

A simple way of tweaking the accuracy of the calculation is via the NumericalQuality key. This sets the quality of several technical aspects of a Band calculation (with the notable exception of the basis set)

NumericalQuality [Basic | Normal | Good | VeryGood | Excellent]

NumericalQuality

Type:

Multiple Choice

Default value:

Normal

Options:

[Basic, Normal, Good, VeryGood, Excellent]

Description:

Set the quality of several important technical aspects of a BAND calculation (with the notable exception of the basis set). It sets the quality of: BeckeGrid (numerical integration), ZlmFit (density fitting), KSpace (reciprocal space integration), and SoftConfinement (basis set confinement). Note: the quality defined in the block of a specific technical aspects supersedes the value defined in NumericalQuality (e.g. if I specify ‘NumericalQuality Basic’ and ‘BeckeGrid%Quality Good’, the quality of the BeckeGrid will be ‘Good’)