Magnetic circular dichroism: *CCMCD

This section deals with the calculation of the ${\cal{B}}(o\!\to\!f)$ term of magnetic circular dichroism for a dipole-allowed transition between the ground state $o$ and the excited state $f$. The ${\cal{B}}(o\to f)$ term results from an appropriate combination of products of electric dipole one-photon transition moments and mixed electric dipole-magnetic dipole two-photon transition moments-- or, more precisely, a combination of transition strengths $S_{AB,C}^{of}(0.0)$-- which are related to the single residues of the (linear and) quadratic response functions [17,190,191]:

$${\cal{B}}(o\to f) \propto \varepsilon_{\alpha\beta\gamma} M^{\mu_\gamma m_\beta}_{of}(0.0)M^{\mu_\alpha}_{fo}$$

Within *CCMCD we specify the keywords needed in order to compute the individual contributions for each chosen transition $(o\to f)$ to the ${\cal{B}}(o\to f)$ term. *CCMCD has to be used in connection with *CCEXCI for the calculation of excited states. The calculation is implemented for the models CCS, CC2 and CCSD. Note that the output results refer to the magnetic moment operator.

.MCD

All six triples of operators obtained from the permutations of 3 simultaneously different Cartesian components of the 3 operators LABELA,LABELB,LABELC are automatically specified. Operator triples which do not correspond to symmetry-allowed combinations will be ignored during the calculation. This is the default.

.OPERAT

READ (LUCMD,'(3A)') LABELA, LABELB, LABELC
DO WHILE (LABELA(1:1).NE.'.' .AND. LABELA(1:1).NE.'*')
READ (LUCMD,'(3A)') LABELA, LABELB, LABELC
END DO

Manually select the operator label triplets defining the operator Cartesian components involved in the ${\cal B}$ term. The first two operators (LABELA,LABELB) are those that enter the two-photon moment. The third operator (LABELC) is the one that enters the one-photon moment. They could be any of the (one-electron) operators for which integrals are available in **INTEGRALS. Specifically for the ${\cal{B}}$ term, LABELA corresponds to any component of the electric dipole moment operator, LABELB a component of the angular momentum (magnetic dipole) and LABELC to a component of the electric dipole. Operator triples which do not correspond to symmetry allowed combination will be ignored during the calculation.

.PRINT

READ (LUCMD,*) IPRINT
Sets the print level in the *MCDCAL section. Default is IPRINT=0.

.SELSTA

READ (LUCMD,'(A70)') LABHELP
DO WHILE (LABHELP(1:1).NE.'.' .AND. LABHELP(1:1).NE.'*')
READ(LABHELP,*) IXSYM,IXST
END DO

Manually select one or more given excited states $f$ among those specified in *CCEXCI. The symmetry (IXSYM) and state number (IXST) within that symmetry are then given, one pair (IXSYM,IXST) per line. Default is all dipole allowed states for all symmetries specified in *CCEXCI.