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I am trying to calculate the excited states using single reference CISD on $\ce{CH3OH},$ using ORMAS' CI-X option in GAMESS. As a test example I am using the $\ce{CH3OH}$ that has 2 core, 7 occ. valence, 39 empty MOs (50 AOs, 48 MOs). I am unable to understand the $ormas flag in the following ormas-meoh-cisd.inp file:

!   single reference CISD on CH3OH, using ORMAS' CI-X option.
!          counting: 2 core, 7 occ. valence, 39 empty MOs (50 AOs, 48 MOs)
!          the resulting CI-SD has 53,964 Sz=0 A' determinants
!
 $contrl scftyp=rhf cityp=ormas runtyp=energy ispher=1 $end
 $system mwords=50 $end
 $basis  gbasis=ccd $end
 $guess  guess=huckel $end
 $scf    dirscf=.true. $end
 $trans  dirtrf=.true. $end
 $cidet  group=Cs stsym=Ap ncore=2 nact=46 nels=14 nstate=3 $end
 $ormas  nspace=2 mstart(1)=3,10 mine(1)=12,0
                                 maxe(1)=14,2 $end
 $data
Methanol...CISD...RHF/6-31G(d) geometry
Cs

H     1.0  -1.0616171503   0.8036449245   0.0000000000
O     8.0  -0.6870131482  -0.0653470836   0.0000000000
C     6.0   0.7093551399   0.0291827007   0.0000000000
H     1.0   1.0836641283   0.5408321444   0.8835398105
H     1.0   1.0975386849  -0.9797829903   0.0000000000
 $end

The following keywords are used in the $ORMAS section:

nspace=2
mstart(1)=3,10
mine(1)=12,0
maxe(1)=14,2

I can understand the nspace = 2 means the active space is partitioned into doubly occupied + active and valence orbitals. However, I don't understand how the numbers pertinent to the rest of the flags in $ORMAS are chosen. Any explanation would be really helpful and appreciated.

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  • $\begingroup$ It seems you may have accidentally made a second account. You can use this form to request that they be merged together. $\endgroup$ – Tyberius May 14 at 16:12

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