MOLPRO

21 MULTIREFERENCE RAYLEIGH SCHRÖDINGER PERTURBATION THEORY 173
RS2,SHIFT=0.2,IGNORE
OPTG
Any publications employing the CASPT2 gradients should cite the above paper. A citation for
MS-CASPT2 gradient method is P. Celani and H.-J. Werner, to be published.
Example:
CASPT2 geometry optimizations for H 2 O:
***
memory,8,m
gthresh,energy=1.d-10
!
basis=vdz
R=2.0
R0=R
Theta=100
geometry={O
H1,O,R;
H2,O,R,H1,THETA}
hf;accu,12
{multi;closed,2}
rs2,shift=0.3,ignoreshift !ignore shift in computing gradient, i.e., no cp-caspt2
optg,gradient=1.d-5
e_opt(1)=energy
r_opt(1)=r
theta_opt(1)=theta
method(1)=’rs2,analytical,ignore’
rs2,shift=0.3
!exact gradient with shift
optg,gradient=1.d-5
e_opt(2)=energy
r_opt(2)=r
theta_opt(2)=theta
method(2)=’rs2,analytical,exact’
rs2,shift=0.3
!numerical gradient with shift
optg,gradient=1.d-5,numerical,fourpoint !use four-point numerical gradient
e_opt(3)=energy
r_opt(3)=r
theta_opt(3)=theta
method(3)=’rs2,numerical’
rs2c,shift=0.3
optg,gradient=1.d-5,fourpoint
e_opt(4)=energy
r_opt(4)=r
theta_opt(4)=theta
method(4)=’rs2c,numerical’
!numerical gradient of rs2c with shift
!use four-point numerical gradient
table,method,r_opt,theta_opt,e_opt
digits,,4,4,8
http://www.molpro.net/info/current/examples/h2o_caspt2_opt.com
This produces the Table
METHOD R_OPT THETA_OPT E_OPT