Molcas Forum

yasuharushiraishi

Member

Registered: 2018-05-14

Posts: 6

Casscf calculation problem (energy and configuration)

Hello,
I try CASSCF(14,10) calculation of molecule which consist of 26 atoms.
Symmetry of molecule is C1, I try calculation of S0 (ground state) and S1 (excited state).

The result of the calculation is as follows

      printout of CI-coefficients larger than  0.05 for root  1
      energy=    -648.085879
      conf/sym  1111111111     Coeff  Weight
             2  222222ud00  -0.94773 0.89819

      printout of CI-coefficients larger than  0.05 for root  2
      energy=    -648.061354
      conf/sym  1111111111     Coeff  Weight
             1  2222222000   0.95923 0.92013

From configuration, I think root 2 is ground state configuration (2222222000),
and root 1 is excited state configuration (222222ud00).
The energy of root 2 is higher than that of root 1,
so ground state energy is higher than excited state energy.

How should I appreciate this result ?
or my calculation is failed?

Best regards.

-My input file is as follows-

&GATEWAY
coord
26
coordinate of 26 atoms
group=c1
basis=6-31G**
&SEWARD
&SCF
&RASSCF
Title
6-31G**
symmetry = 1
Nactel = 14 0 0
Spin = 1
Inactive = 44
Ras2 = 10
CIroot = 2 2; 1 2; 1 1

Ignacio

Administrator

From: Uppsala

Registered: 2015-11-03

Posts: 1,085

Re: Casscf calculation problem (energy and configuration)

From configuration, I think root 2 is ground state configuration (2222222000),
and root 1 is excited state configuration (222222ud00).

You got it wrong, or confused. The ground state is the lower energy, by definition. 2222222000 is just the closed-shell configuration (for those particular orbitals, change the orbitals and the CSFs will look different). What you got is a set of orbitals for which the ground state (or the lowest singlet) has an open-shell configuration, maybe not the most common but not something to be scared of.