MOLPRO

41 ENERGY GRADIENTS 299
If this card is present, the current gradient and energy are scaled by the give factor. This is
sometimes useful for the optimization of counterpoise corrected energies (cf. 42.4.7).
41.1.3 Defining the orbitals for SCF gradients (ORBITAL)
ORBITAL,record.file;
In the SCF case, record.file specifies the location of the orbitals, which are used for constructing
density matrices, etc. This card is only needed if the SCF for which the gradient is to be
computed was not the most recent energy calculation.
For MCSCF wavefunctions, the ORBITAL card is not needed, because the location of the orbitals
is stored in the MCSCF dump record.
41.1.4 MCSCF gradients (MCSCF)
MCSCF,record.file;
Triggers code for MCSCF gradient. record.file specifies the location of information dumped
from the MCSCF program, using a SAVE,GRD=recmc.filmc card. This card is not needed if
the FORCE command appears directly after the corresponding MCSCF input, since the program
automatically remembers where the MCSCF information was stored. The same is true if OPTG
is used.
41.1.5 State-averaged MCSCF gradients with SEWARD
SA-MCSCF gradients can be computed using segmented or generally contracted basis sets using
SEWARD and the RS2 gradient program. The NOEXC directive has to be used in the RS2 input,
but no CPMCSCF card is required in MULTI. The RS2 gradient program does the CP-MCSCF
automatically.
Example: compute SA-CASSCF gradients for 2 Π and 2 Σ + state of OH.
geometry={o;h,o,r}
r=1.83
{multi;wf,9,2,1;wf,9,3,1;wf,9,1,1}
{rs2;noexc;wf,9,1,1}
forces
{rs2;noexc;wf,9,2,1}
forces
!state averaged casscf for X(2PI) and A(2SIGMA)
!compute A(2SIGMA) energy
!energy gradient for A(2SIGMA) state
!compute A(2PI) energy
!energy gradient for A(2PI) state
http://www.molpro.net/info/current/examples/oh_samcforce.com
Without the NOEXC directive, the RS2 (CASPT2) gradient would be evaluated, using the stateaveraged
orbitals.
41.1.6 State-averaged MCSCF gradients with CADPAC
Normally, no further input is required for computing gradients for state-averaged MCSCF when
CADPAC is used. Note, however, that a CPMCSCF,GRAD,state directive is required in the SA-
MCSCF calculation (see Section 19.9). The gradients are then computed automatically for the
state specified on the CPMCSCF card. The same is true for difference gradients (CPMCSCF,DGRAD,state1,