39.1.6 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 20.9). The gradients are then computed automatically for the state specified on the CPMCSCF card. The same is true for difference gradients (CPMCSCF,DGRAD,state1, state2) and non-adiabatic coupling matrix elements (CPMCSCF,NACM,state1, state2). It is possible to do several coupled-perturbed MCSCF calculations one after each other in the same MCSCF. In this case FORCE would use the last solution by default. The information from the CPMCSCF is passed to the FORCE program in a certain records (default 5101.1, 5102.1, ...). If several CPMCSCF calculations are performed in the same MCSCF, several such records may be present, and a particular one can be accessed in the FORCE program using the SAMC directive:

SAMC,record.

An alias for SAMC is CPMC. For compatibility with earlier versions one can also use

NACM,record

for non-adiabatic couplings or

DEMC,record

for difference gradients.

Example:

multi;
....
state,3
cpmcscf,nacm,1.1,2.1,save=5101.1   !do cpmcscf for coupling of states 1.1 - 2.1
cpmcscf,nacm,1.1,3.1,save=5102.1   !do cpmcscf for coupling of states 1.1 - 3.1
cpmcscf,nacm,2.1,3.1,save=5103.1   !do cpmcscf for coupling of states 2.1 - 3.1

force;samc,5101.1;                 !compute NACME for states 1.1 - 2.1
force;samc,5102.1;                 !compute NACME for states 1.1 - 3.1
force;samc,5103.1;                 !compute NACME for states 2.1 - 3.1

See also test job lif$_-$nacme.test.