21.1.2 Options for the diagonalization method

In calculations with very large basis sets, the diagonalization time becomes a significant fraction of the total CPU time. This can be reduced using the orbital rotation method as described in R. Polly, H.-J. Werner, F. R. Manby, and Peter J. Knowles, Mol. Phys. 102, 2311 (2004))

MINROT=minrot

If minrot$\ge 0$, the orbital rotation method is employed. Explicit diagonalization of the full Fock matrix is performed in the first minrot iterations and in the last iteration. If minrot=0, a default is used which depends on the starting guess.

NEXPR=nexpr

Number of terms used in the exponential expansion of the unitary orbital transformation matrix (default 4).

DEROT=nexpr

Energy gap used in the orbital rotation method. For orbitals within $\pm$derot hartree of the HOMO orbital energy the Fock matrix is constructed and diagonalized (default 1.0)

JACOBI=jacobi

If nonzero, use Jacobi diagonalization.