20.6.2 Selecting the orbital optimization method

The ITERATIONS directive can be use to modify the defaults for the optimization method. It consists of a sequence of several cards, ending with an END card.

ITERATIONS;
DO,method1,iter1[,TO,iter2];
DONT,method2,iter3[,TO,iter4];
$\ldots$
END;

method can be one of the following:

DIAGCI

Diagonalize hamiltonian in the beginning of the specified iterations. This is the default for iteration 1.

INTERNAL

Optimize internal orbitals at the beginning of the specified iterations. This is default for second and subsequent iterations.

WERNER

use Werner-Meyer-Knowles non-linear optimization method for the specified iterations. This is the default for all iterations.

AUGMENT

Use step-restricted Augmented Hessian method for the specified iterations.

NEWTON

Use Newton-Raphson method for specified iterations.

UNCOUPLE

Do not optimize orbitals and CI coefficients simultaneously in the specified iterations. This option will set DIAGCI for these iterations.

NULL

No orbital optimization.