Molcas Forum

yasuharushiraishi

Member

Registered: 2018-05-14

Posts: 6

Casscf calculation problem (same molecule, but use different symmetry)

Hello,
I try CASSCF(14,13) calculation of molecule which consist of 42 atoms.
Symmetry of molecule is C2h, I try calculation of S0 (ground state) and S1 (excited state).

I try S0 (Ag) and S1 (B2u) calcaulation by state-specific CASSCF(14,13) (molcule symmetry C2h),
and I try S0 (A) and S1 (A) calcaulation by 2 state-averaged CASSCF(14,13) (molcule symmetry C1).

Although molecue is same, calculation result by C2h symmetry is
different from calculation result by C1 symmerty.

I think calculation result by C1 symmetry is local minimum,
but I don’t know how to get global minimum result by C1 symmetry.
Best regards.

My calculation result and iput file is as follows.

(1) CASSCF(14,13) calculation result by C2h symmetry
(a) energy and configuration of S0 (symmetry Ag) state

      printout of CI-coefficients larger than  0.05 for root  1
      energy=   -1712.716659
      conf/sym  2222222 333333     Coeff  Weight
        158505  2220000 222200   0.88562 0.78432

     
(b) energy and configuration of S1 (symmetry Bu) state

      printout of CI-coefficients larger than  0.05 for root  1
energy=   -1712.621610
      conf/sym  2222222 333333     Coeff  Weight
         77895  222u000 222d00   0.88608 0.78513

(2) CASSCF(14,13) calculation result by C1 symmetry
(a) energy and configuration of S0 state (symmetry A, root 1) and S1 state (symmetry A, root 2)

      printout of CI-coefficients larger than  0.05 for root  1
      energy=   -1712.732197
      conf/sym  1111111111111     Coeff  Weight
             1  2222222000000  -0.65215 0.42530
             2  222222ud00000  -0.58613 0.34355
      printout of CI-coefficients larger than  0.05 for root  2
      energy=   -1712.631232
      conf/sym  1111111111111     Coeff  Weight
             1  2222222000000   0.53674 0.28809
             2  222222ud00000  -0.57871 0.33491

(3) input file of molecule (symmetry C2h)-

&GATEWAY
coord
42
coordinate of 42 atoms
group=XY XYZ
basis=cc-pVDZ
&SEWARD
&SCF
&RASSCF
Title
cc-pVDZ
symmetry = 1 (Ag) or 4 (B2u) 
Nactel = 14 0 0
Spin = 1
Inactive = 38 5 5 38
Ras2 = 0 7 6 0

(4) input file of molecule (symmetry C1)

&GATEWAY
coord
42
coordinate of 42 atoms
group=C1
basis=cc-pVDZ
&SEWARD
&SCF
&RASSCF
Title
cc-pVDZ
symmetry = 1
Nactel = 14 0 0
Spin = 1
ALTER = 4
1 85 87
1 86 90
1 98 100
1 99 103
Inactive = 86
Ras2 = 13
CIroot = 2 2; 1 2; 1 1;

Ignacio

Administrator

From: Uppsala

Registered: 2015-11-03

Posts: 1,085

Re: Casscf calculation problem (same molecule, but use different symmetry)

Since the C1 energy is lower than C2h, it would rather seem that it is the C2h that s a local minimum, and maybe with C1 you get a broken-symmetry solution.