I am very confused about the setting of the spin number in CDFT. This is an example from the manual, why is the spin number set to -1.0 here? How should understand positive and negative numbers in here?
$molecule
-1 1
C -1.453000 -1.953000 -0.264000
N -0.278000 -1.402000 -0.440000
N -1.804000 -2.052000 1.091000
C -0.687000 -1.548000 1.806000
O -0.688000 -1.514000 3.031000
C 0.291000 -1.140000 0.799000
C 1.500000 -0.563000 1.254000
H 1.585000 -0.660000 2.346000
C 2.608000 0.030000 0.605000
C 2.763000 0.182000 -0.865000
H 1.926000 -0.073000 -1.543000
C 3.733000 0.548000 1.313000
H 3.682000 0.571000 2.326000
C 3.821000 0.875000 -1.473000
H 3.844000 1.102000 -2.575000
C 4.938000 1.111000 0.700000
H 5.734000 1.441000 1.308000
C 5.037000 1.228000 -0.739000
O 6.011000 1.818000 -1.261000
C -3.000000 -2.533000 1.832000
H -2.859000 -2.250000 2.892000
H -3.829000 -2.121000 1.354000
C -2.373000 -2.282000 -1.448000
H -1.790000 -3.026000 -2.045000
H -2.626000 -1.300000 -1.865000
H -3.054000 -3.631000 1.855000
H -3.308000 -2.854000 -1.357000
C 7.648000 -5.429000 0.303000
H 8.028000 -4.514000 0.845000
H 7.274000 -5.098000 -0.671000
C 6.499001 -5.986000 1.016000
C 6.462999 -6.032001 2.390000
H 7.284000 -5.579000 2.957000
C 5.243000 -6.435000 3.018000
H 5.190001 -6.315001 4.035000
C 4.242001 -7.048000 2.189000
O 3.095000 -7.615000 2.715000
H 2.500999 -7.869000 1.979000
C 5.454000 -6.469000 0.200000
H 5.565001 -6.363000 -0.835000
C 4.294001 -7.003000 0.803000
H 3.469000 -7.324000 0.139000
H 8.511000 -6.108000 0.245000
$end
$rem
SYMMETRY = off
SYM_IGNORE = true
METHOD = b3lyp
BASIS = cc-pvdz
UNRESTRICTED = true
SCF_CONVERGENCE = 8
MAX_SCF_CYCLES = 200
CDFTCI = true
CDFTCI_PRINT = 2
CDFT_THRESH = 7
$end
$cdft
1.0
1.0 1 27
0.0
1.0 1 27 S
0.0
1.0 1 27
-1.0
1.0 1 27 S
$end
Hope to receive a reasonable answer.