Dear all,
I have found that if I change the weight of each state, the SA-CASSCF result seems right. My first try is to assign equal weight for ground state and the total other 35 single excited states (both for SA-CASSCF and MS-MR-CASPT2), but I find it is hard to use all orbitals in MS-MR-CASPT2, I think the dynamic correlation between f otbitals and Inner orbitals may be very small, so I freeze all occupied orbitals except the 7 f-orbitals, this is the input:
{df-multi
MAXITER,400
closed,140
occ,152
wf,287,1,7
start,2110.2
state,36;WEIGHT,1,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143
canonical}
{df-rs2c,shift=0.1,IPEA=0.3,mix=36,xms=1,noprop,maxit=100,maxiti=400
closed,140
occ,152
core,140
wf,287,1,7
state,36;WEIGHT,1,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143,0.02857143}
the SA-CASSCF result reveals the first state is 4f^7 state and the others are excited state, and the energy gap is 0.095 hartree which is relatively closed to the experimental value (~0.11 hartree), but the energy gap in MS-MR-CASPT2 result is 0.075 hartree which is not right. And I also calculate only 2 state, although it take far more number of iterations to converge, but the reasult seems more reasonable. SA-CASSCF reveals the 2 states are 4f^7 and 4f^6 5d^1, the energy gap is 0.088 hartree in SA-CASSCF and 0.106 hartree in MS-MR-CASSCF which is extremely closed to the experimental value (~0.11 hartree), this is the input,
{multi,SO_SCI
MAXITER,400
closed,140
occ,152
wf,287,1,7
start,2110.2
state,2
canonical}
{rs2c,shift=0.1,IPEA=0.3,mix=2,xms=1,maxit=100,maxiti=400
closed,140
occ,152
core,140
wf,287,1,7
state,2}
I am not sure about those results, and I want to ask that,
1) Using only 2 states in SA-CASSCF and MS-MR-CASPT2 seems right although the number of iterations (129) to converge SA-CASSCF is far more than 36 states (14). So is it OK to use 2 states results?
2) The dynamic correlation effects in the two calculation behaves totally different which decrease energy gap 0.02 hartree in 36 states while increase 0.018 hartree in 2 states. So I guess I may make some mistakes in MS-MR-CASPT2 calculation?
3) I read the paper about the dynamically weighted MCSCF(
https://doi.org/10.1063/1.1667468), I have a question that if we change the weight according to the energy gap which influence the final energy of each state, so shall this method lead the dynamic correlation effects into MCSCF calculation artificially? Will this influence the results of the next MS-MR-CASPT2 calculation?
Really hope you can give me some suggestions about this, thanks a lot.