Precision and Self-Consistency¶

The precision of a calculation is determined by

• The function sets (basis sets, levels of frozen core approximation, and fit sets for the computation of the Coulomb potential)

• Numerical integration settings in real space

• The accuracy of the density fitting procedure

• Convergence criteria (for the SCF procedure and the geometry optimization)

• A few more items that are rather technical and usually irrelevant (these are not discussed here).

The fragments you attach determine, through the fragment files, the function sets. Since each fragment traces back to one or more Create runs, the employed database files in the Create runs determine the function sets that are ultimately used.

In this section we examine numerical integration, density fitting, and the SCF procedure.

Numerical Quality

With the key NUMERICALQUALITY one can set the density fitting quality (ZlmFit) and the numerical integration quality (BeckeGrid) simultaneously.

NUMERICALQUALITY [basic|normal|good|verygood|excellent]

Note that the so-called Excellent quality is only meant for debugging purposes. In case of real numerical issues the results with Excellent should not be trusted more than those with VeryGood.