Hello all,
I wonder how to set the ras_nfrag_sets. I’m using q-chem 6.0.2 windows version.
Take the following ethylene input file as an example.
$molecule
0 1
C 0.000000 0.000000 0.665547
C 0.000000 0.000000 -0.665547
H 0.000000 0.923577 1.239710
H 0.000000 -0.923577 1.239710
H 0.000000 -0.923577 -1.239710
H 0.000000 0.923577 -1.239710
C 3.500000 0.000000 0.665547
C 3.500000 0.000000 -0.665547
H 3.500000 0.923577 1.239710
H 3.500000 -0.923577 1.239710
H 3.500000 -0.923577 -1.239710
H 3.500000 0.923577 -1.239710
$end$rem
MEM_TOTAL 24000
MEM_STATIC 100
jobtype sp
exchange hf
basis 6-31G
max_cis_cycles 50
correlation rasci
ras_roots 14
ras_act 4
ras_elec 4
ras_occ 14
ras_spin_mult 1
ras_print 2
set_iter 1000
molden_format true
print_orbitals 10
$end
the output file is like
- RAS-CI Dimensions
- Active Elec.: 4 ( 2, 2) Active Orb.: 4 *
- Doubly Occ. : 14 Doubly Vir.: 34 *
- Frozen Occ. : 0 Frozen Vir.: 0 *
- Total CI configurations: 2340 *
- Active configurations: 36 *
Hole configurations: 672 *- Particle configurations: 1632 *
- Requested states: 14 *
- Spin multiplicity: Singlets *
if I set
ras_nfrag 2
ras_nfrag_atoms [6,6]
ras_nfrag_sets [4,10,15,17,19]
q-chem can work.
But I don’t know why.
According to RAS-2SF Exciton decomposition - Questions - Q-Chem Talk
and The manual “Defines the number of orbitals in each disjoint set to perform orbital localization”,“[NOcc,NAct,NVir]”
I think ras_nfrag_sets is [core orbital of RAS1, residual RAS1’, RAS2,RAS2’, RAS3,RAS3’,RAS3’’],
while RAS1,residual RAS1 are two fragments in ras1 (RAS1+RAS1’=ras_occ=14); RAS2, RAS2’ are two fragments in ras2(ras2+ras2’=ras_act=4); and RAS3’+RAS3’=virtual number=34
but if i set ras_nfrag_sets [4,10,2,2,17,17] ,the software doesn’t work.
So how to set ras_nfrag_sets? Why [4,10,2,2,17,17] is wrong and why [4,10,15,17,19] can work?
Thank you.