Multi-state caspt2 calculations are only possible with the `rs2` program.

There are various possibilities how to choose the zeroth-order Hamiltonian and the configuration basis. Here we describe only the recommended method; for more details see manual.

Three options are relevant:

`rs2,xms=`*value*,`mix=`*nstates*,`root=`*iroot*

where

`xms=0`:- MS-CASPT2 method of Finley et al. CPL 288, 299 (1998)
`xms=1`:- Extended multi-state CASPT2 (XMS-CASPT2) method as described in J. Chem. Phys.
**135**, 081106 (2011). fully invariant treatment of level shifts (recommended). `xms=2`:- XMS-CASPT2 method; level shift is only applied to the diagonal of H0.
*nstates*:- Number of states included in the calculation
*iroot*:- Root number to be optimized in subseqent gradient calculation (only required if gradient calculations follows)

Example:

***,mscaspt2 for h2o 3B2 states basis=vdz geometry={O H1,O,R; H2,O,R,H1,THETA} R=2.4 Theta=98 hf {multi;closed,2 wf,10,1,2;state,3 !three 3A1 states included in sa-casscf wf,10,2,2;state,2 !two 3B1 states included in sa-casscf wf,10,3,2;state,3 !three 3B2 states included in sa-casscf canonical,2140.2} !save pseudo canonical orbitals {rs2,xms=2,mix=3,root=2; !include three B2 states, !select the second state for gradients wf,10,3,2} !Triplet B2 state symmetry optg !optimize the geometry

molpro@molpro.net 2018-12-18