MOLPRO

16 THE SCF PROGRAM 104
r1=1.85,r2=1.85,theta=104
!set geometry parameters
geometry={O;
!z-matrix geometry input
H1,O,r1;
H2,O,r2,H1,theta}
basis=vdz
hf
!scf using c2v symmetry
orbital,2100.2 !save on record 2100.2
symmetry,x
hf
start,2100.2
orbital,2101.2
geometry={O;
H1,O,r1;
H2,O,r2,H1,theta}
symmetry,x,y
hf
start,2101.2
orbital,2102.2
!start with previous orbitals from c2v symmetry
!save new orbitals
! geometry has to be respecified so that
! H1 and H2 can be retagged as symmetry related
!start with orbitals from cs symmetry
save new orbitals
http:
//www.molpro.net/info/current/examples/h2o_c2v_cs_start.com
Note, however, that this only works well if the orientation of the molecule does not change.
Sometimes it might be helpful to use the noorient option.
Note also that a single dump record cannot hold orbitals for different basis dimensions. Using
save=2100.2 in the second calculation would therefore produce an error.
If orbitals from a corresponding SCF calculation at a neighbouring geometry are available, these
should be used as starting guess.
16.4.3 Starting with a previous density matrix
START,DENSITY=record.file,[specifications]
A density matrix is read from the given dump record and used for constructing the first fock
matrix. A specific density matrix can be specified as described in section 4.11. It is normally
not recommended to use the DENSITY option.
16.5 Rotating pairs of orbitals
ROTATE,orb 1 .sym,orb 2 .sym,angle
Performs a 2×2 rotation of the initial orbitals orb 1 and orb 2 in symmetry sym by angle degrees.
With angle= 0 the orbitals are exchanged. See MERGE for other possibilities to manipulate
orbitals. In UHF, by default only the β-spin orbitals are rotated. The initial α-spin orbitals can
be rotated using
ROTATEA,orb 1 .sym,orb 2 .sym,angle
In this case ROTATEB is an alias for ROTATE.