MOLPRO

42 GEOMETRY OPTIMIZATION (OPTG) 319
Three sets of FORCE commands (only two for Singlet/Triplet intersection) follow the MULTI
input. They will be like:
FORCE
SAMC,record[n].file
CONICAL,record4.file[,NODC]
where record.file is one of the records containing CPMCSCF info and record4.file points to a
free record used for internal storage by the CONICAL code. record4.file must be the same on
all the CONICAL directives. Furthermore, the present implementation works properly only if
file=1 on the CONICAL directive. The optional keyword NODC must be used in case of different
spins (e.g., S/T crossing) when DC is not needed.
The actual optimization is performed using OPTG,STARTCMD=MULTI The example below
optimizes the conical intersection in LiH 2 (ground and excited states are both doublets).
***, LiH2
basis=sto-3g
print,orbitals,civector
symmetry,x
!use only molecular plane. Both states must be in the same symmetry.
geometry={
Li;
h1,Li,r;
h2,Li,r,h1,theta}
r=3.0
theta=35
{hf;wf,4,1,0}
{multi;occ,6,1;wf,5,1,1;state,2
!state averaged casscf
CPMCSCF,NACM,1.1,2.1,accu=1.0d-7,record=5100.1 !cpmcscf for non-adiabatic couplings
CPMCSCF,GRAD,1.1,spin=0.5,accu=1.0d-7,record=5101.1 !gradient for state 1
CPMCSCF,GRAD,2.1,spin=0.5,accu=1.0d-7,record=5102.1} !gradient for state 2
{Force
SAMC,5100.1
CONICAL,6100.1}
!compute coupling matrix element
!save information for optimization of conical intersection
{Force
SAMC,5101.1 !compute gradient for state 1
CONICAL,6100.1}
!save information for optimization of conical intersection
{Force
SAMC,5102.1 !compute gradient for state 2
CONICAL,6100.1}
!save information for optimization of conical intersection
optg,startcmd=multi
!find conical intersection
http://www.molpro.net/info/current/examples/lih2_D0D1.com
This second example optimizes the singlet-triplet intersection in LiH 2 (+) (ground state is Singlet,
excited state is Triplet).