star(QUADRATIC RESPONSE)

This section gives directives for the calculation of quadratic response functions [Saue2002a].

General control statements

keyword(PRINT)

Print level.

Default:

.PRINT
 0

Definition of the quadratic response function

keyword(DIPLEN)

Specification of dipole operators for A, B, and C (see One-electron operators for details).

keyword(A OPERATOR)

Specification of the A operator (see One-electron operators for details).

keyword(B OPERATOR)

Specification of the B operator (see One-electron operators for details).

keyword(C OPERATOR)

Specification of the C operator (see One-electron operators for details).

keyword(B FREQ)

Specify frequencies of operator B.

Example: 3 different frequencies.

.B FREQ
 3
 0.001
 0.002
 0.01

Default: Static case.

.B FREQ
 1
 0.0

keyword(C FREQ)

Specify frequencies of operator C (see QUADRATIC_RESPONSE_.B FREQ).

keyword(ALLCMB)

Evaluate all nonzero quadratic response functions and thereby disregarding analysis of overall permutational symmetry.

Default: Evaluate only unique, nonzero, response functions.

Excited state properties

This page describes unreleased functionality. The keywords may not be available in your version of DIRAC.

First order properties of excited states can be computed from the quadratic response function.

keyword(EXCPRP)

Give the number of “left” and “right” states in each boson symmetry.

Example:

.EXCPRP
5 5 5 5
0 0 0 0

Compute the excited state expectation values |\langle i|\hat{A}|i\rangle|, where i goes from 1 to 5 in each symmetry (four symmetries in this case). The zeros can be substituted with positive integers to generate transition state moments |\langle i|\hat{A}|j\rangle|.

Control variational parameters

keyword(SKIPEE)

Exclude all rotations between occupied positive-energy and virtual positive-energy orbitals.

keyword(SKIPEP)

Exclude all rotations between occupied positive-energy and virtual negative-energy orbitals.

Control reduced equations

keyword(MAXITR)

Maximum number of iterations.

Default:

.MAXITR
 30

keyword(MAXRED)

Maximum dimension of matrix in reduced system.

Default:

.MAXRED
 100

keyword(THRESH)

Threshold for convergence of reduced system.

Default:

.THRESH
 1.0D-5

Control integral contributions

The user is encouraged to experiment with these options since they may have an important effect on run time.

keyword(INTFLG)

Specify what two-electron integrals to include (default: HAMILTONIAN_.INTFLG under **HAMILTONIAN).

keyword(CNVINT)

Set threshold for convergence before adding SL and SS integrals to SCF-iterations.

2 (real) Arguments:

.CNVINT
 CNVXQR(1) CNVXQR(2)

Default: Very large numbers.

keyword(ITRINT)

Set the number of iterations before adding SL and SS integrals to SCF-iterations.

Default:

.ITRINT
 1 1

Control trial vectors

keyword(XQRNRM)

Normalize trial vectors. Using normalized trial vectors will reduce efficiency of screening.

Default: Use un-normalized vectors.

Advanced/debug flags

keyword(NOPREC)

No preconditioning of initial trial vectors.

Default: Preconditioning of trial vectors.

keyword(RESFAC)

New trial vector will be generated only for variational parameter classes whose residual has a norm that is larger than a fraction 1/RESFAC of the maximum norm.

Default:

.RESFAC
 1000.0