Cubic response calculation of third-order transition moments: *CUBIC with .SINGLE RESIDUE

Calculation of single residues of cubic response functions [169,170,90]. $A,B$,$C$, and $D$-named options refer to the operators in the cubic response function $\langle\!\langle A;B,C,D\rangle\!\rangle_{\omega_b,\omega_c,\omega_d}$

.APROP, .BPROP, .CPROP

Specify the operators $A$, $B$, and $C$, respectively. The line following this option should be the label of the operator as it appears in the file AOPROPER.

.BFREQ, .CFREQ

The frequencies $\omega_b$ and $\omega_c$, respectively. Input as in .FREQUE.

.DIPLEN Sets $A$, $B$, $C$, and $D$ to dipole operators.

.DIPLNX Sets $A$, $B$, $C$, and $D$ to the $x$ dipole operator.

.DIPLNY Sets $A$, $B$, $C$, and $D$ to the $y$ dipole operator.

.DIPLNZ Sets $A$, $B$, $C$ and $D$ to the $z$ dipole operator.

.FREQUE
READ *, NFREQ
READ *, FREQ(1:NFREQ)
Sets the frequencies whenever a optical process is specified. Can also be used for the residue calculation in which case it sets both $\omega_b$ and $\omega_c$ for the single residue and only $\omega_b$ for the double residue.

.MAX IT Maximum number of iterations for solving linear equations, default value is 60.

.MAXITO Maximum number of optimal orbital trial vector microiterations, default value is 5.

.MAXITP Maximum number of iteration for solving eigenvalue equation, default value is 60.

.NOHG Do not restrict the calculation to the 'harmonic generation case', that is, allow a different number and different numerical values for the frequencies of the $B$ and $C$ operators. By default, it is assumed that the $B$ and $C$ operator frequencies are identical.

.PRINT Print flag for output, default value is 2. Timer information is printed out if print flag greater than 5. Response vectors printed out if print flag greater than 10.

.ROOTS Number of roots (excited states) to converge.
READ (LUCMD,*) (NTMCNV(J),J=1,NSYM)

.SINGLE Computes the single residue of the cubic response function. In the case of dipole operators this corresponds to three-photon absorption.

.THCLR Threshold for convergence of response vectors, default value is $10^{-3}$.

.THCPP Threshold for convergence of eigenvector, default value is $10^{-3}$.

.THREE-PHOTON Sets up the calculation of the three-photon transition strengths. This calculates two-photon transition strengths for all the excited states requested by the keyword .ROOTS, calculating the necessary cubic response functions using a third of the frequency of the excitation energy to the given state.