MOLPRO

37 NON ADIABATIC COUPLING MATRIX ELEMENTS 271
***,H2S diabatic A" states
basis=VDZ
symmetry,x,planeyz
orient,noorient
geometry={s;h1,s,r1;h2,s,r2,h1,theta}
gprint,orbitals,civector
text,reference calculation for C2V
theta=92.12,r1=2.3,r2=2.3
{hf;occ,7,2;wf,18,1}
!use cc-pVDZ basis set
!use Cs symmetry & fix orientation of the molecule
!dont allow automatic reorientation
!Z-matrix geometry input
!global print options
!reference geometry
!scf calculation for ground state
{multi;occ,9,2;closed,4,1;
!define active and inactive spaces
wf,18,2;state,2;
!two A" states (1B1 and 1A2 in C2v)
orbital,2140.2} !save orbitals to 2140.2
reforb=2140.2
text,calculations at displaced geometries
rd=[2.4,2.5,2.6]
do i=1,#rd
r2=rd(i)
{multi;occ,9,2;closed,4,1;
wf,18,2;state,2;
orbital,2141.2
diab,reforb}
reforb=2141.2
enddo
!define a range of bond distances
!loop over displaced geometries
!set r2 to current distance
!same wavefunction definition as at reference geom.
!save new orbitals to record
!compute diabatic orbitals using reference orbitals
!stored on record reforb
!set variable reforb to the new orbitals.
http://www.molpro.net/info/current/examples/h2s_diab.com
37 NON ADIABATIC COUPLING MATRIX ELEMENTS
Non-adiabatic coupling matrix elements can be computed by finite differences for MCSCF or
CI wavefunctions using the DDR program. For state-averaged MCSCF wavefunctions, they can
also computed analytically (cf. section 19.9.2).
Note that present numerical procedure has been much simplified relative to Molpro96. No
GEOM and DISPL input cards are needed any more, and the three necessary calculations can be
done in any order.
37.1 The DDR procedure
In order to compute the coupling matrix elements by finite differences, one has to compute and
store the wavefunctions at two (first-order algorithm) or three (second-order algorithm) slightly
displaced geometries. The order of these calculations is arbitrary.
The typical strategy is as follows:
1.) Compute the wavefunction at the reference geometry. The wavefunctions for both states
have to be stored using the SAVE command of the CI program. If the matrix elements are
computed for MCSCF wavefunctions, it is necessary to recompute the wavefunction with the CI