Molcas Forum

tumitumi123

Member

Registered: 2017-06-13

Posts: 16

casscf for CH3I+ Problems in orbital optimization

Dear all
I want to calculate roughly the CH3I+ potential curve for ground state along CI bond, and check the charge distribution at dissociation limit.
the correct one is CH3^(+)+I. and the orbital at large distance for valence electron(I,7electron;C,4electron) should be:
1a,2a,1pix,1piy,2pix,2piy,3a,4a
at equilibrium the orbital is
1a,2a,1pix,1piy,3a,2pix,2piy,4a
However, in my casscf, at equilibrium the orbital are correct. But at large distance CI=13a.u., the 3a and 2pi orbitals do not change order, and there is
"Problems in orbital optimization
Warning: In symmetry  1, orbital p=  27 has diagonal density matrix element D(p,p) close to two. (2 - D(p,p))=  0.333639D-06"
and the mulliken charge also wrong, it give me CH3+I^(+).

below is my input

&gateway
coord
5
bohr
C    0 0  0
H1   $h1x $h1y $h1z
H2 $h2x $h2y $h2z
H3 $h3x $h3y $h3z
I   0 0 $RCI
basis=ano-rcc-vdz 
*C.CC-PVDZ,H.CC-PVDZ,I.ECP.Stoll.4s5p.2s3p.7e-MWB
group=nosymm
&SEWARD 
&RASSCF
spin=2
nactel=9 0 0
inactive=26
ras2=6
ciroot=4 4 1
symmetry=1 
&GRID_IT

any suggestion is welcomed, thanks a lot

Shan Xue
tumitumi123@phys.ksu.edu
Physics Department, KSU, Mahattan, KS