MOLPRO

19 THE MCSCF PROGRAM MULTI 145
19.9.1 Gradients for SA-MCSCF
For computing state-averaged gradients, use
CPMCSCF,GRAD,state,[SPIN=spin],[MS2=ms2],[ACCU=thresh],[RECORD=record]
where state specifies the state (e.g., 2.1 for the second state in symmetry 1) for which the gradients
will computed. spin specifies the spin of the state: this is half the value used in the
corresponding WF card (e.g., 0=Singlet, 0.5=Doublet, 1=Triplet). Alternatively, MS2 can be
used, where ms2 = 2*spin, i.e., the same as specified on WF cards. The specification of SPIN or
MS2 is only necessary if states with different spin are state-averaged. record specifies a record
on which the gradient information is stored (the default is 5101.1). thresh is a threshold for the
accuracy of the CP-MCSCF solution. The default is 1.d-7.
The gradients are computed by a subsequent call to FORCES or OPTG.
Note: if for some reason the gradients are to be computed numerically from finite energy differences,
it is in state-averaged calculations necessary to give, instead of the CPMCSCF input, the
following:
SAVE,GRAD=-1
Otherwise the program will stop with an error message.
19.9.2 Difference gradients for SA-MCSCF
For computing difference gradients, use
CPMCSCF,DGRAD,state1,state2,[ACCU=thresh],[RECORD=record]
where state1 and state2 specify the two states considered. (e.g., 2.1,3.1 for the second and third
states in symmetry 1) The gradient of the energy difference will be computed. Both states must
have the same symmetry. record specifies a record on which the gradient information is stored
(the default is 5101.1). thresh is a threshold for the accuracy of the CP-MCSCF solution. The
default is 1.d-7.
The gradients are computed by a subsequent call to FORCES or OPTG.
19.9.3 Non-adiabatic coupling matrix elements for SA-MCSCF
For computing non-adiabatic coupling matrix elements analytically, use
CPMCSCF,NACM,state1,state2,[ACCU=thresh],[RECORD=record]
where state1 and state2 specify the two states considered. (e.g., 2.1,3.1 for the second and third
states in symmetry 1) Both states must have the same symmetry. record specifies a record on
which the gradient information is stored (the default is 5101.1). This will be read in the subsequent
gradient calculation. thresh is a threshold for the accuracy of the CP-MCSCF solution.
The default is 1.d-7.
NADC and NADK are an aliases for NADC, and SAVE is an alias for RECORD.
The matrix elements for each atom are computed by a subsequent call to FORCES.
Note: this program is not yet extensively tested and should be used with care!