# Example: NOCV: CH3 – CH3¶

```
#! /bin/sh
# Example for calculation of ETS-NOCV for simulated unrestricted fragments. ETS-NOCV:
# energy analysis using the Natural Orbitals for Chemical Valence. The ethane
# molecule is built from two methyl radicals
# First the two methyl fragments are calculated.
# If the FRAGOCCUPATIONS keyword is used in ethane the fragments should be calculated
# spin-restricted.
AMS_JOBNAME=frag1 $AMSBIN/ams <<eor
System
atoms
C 0.019664 -0.034069 0.009101
H 0.039672 -0.069395 1.109620
H 1.063205 -0.065727 -0.341092
H -0.474230 -0.953693 -0.341621
end
end
Task SinglePoint
Engine ADF
title CH3-CH3 built from CH3 radicals, FULL electron calc.!
basis
Type DZP
Core None
end
scf
converge 1E-6
end
symmetry NOSYM
xc
gga becke perdew
end
Relativity
Level None
End
EndEngine
eor
AMS_JOBNAME=frag2 $AMSBIN/ams <<eor
System
atoms
C -0.703210 1.217999 -0.497874
H -0.723753 1.252869 -1.598316
H -1.746567 1.250049 -0.147169
H -0.208833 2.137544 -0.147653
end
end
Task SinglePoint
Engine ADF
title CH3 radical
basis
Type DZP
Core None
end
scf
converge 1E-6
end
symmetry NOSYM
xc
gga becke perdew
end
Relativity
Level None
End
EndEngine
eor
# Next these fragments are used in the calculation of the molecule ethane, using
# the key FRAGOCCUPATIONS to use an unrestricted fragment occupation for the
# methyl radicals, such that they are prepared for bonding. In the one fragment
# the singly occupied orbital will be an alpha-orbital, and in the other fragment
# the singly occupied orbital will be a beta-orbital, such that the calculated
# Pauli repulsion between the fragments will be small.
# The block key ETSNOCV used here is in its single line form.
# The symmetry must be NOSYM.
$AMSBIN/ams <<eor
System
atoms
C 0.019664 -0.034069 0.009101 adf.f=f1
H 0.039672 -0.069395 1.109620 adf.f=f1
H 1.063205 -0.065727 -0.341092 adf.f=f1
H -0.474230 -0.953693 -0.341621 adf.f=f1
C -0.703210 1.217999 -0.497874 adf.f=f2
H -0.723753 1.252869 -1.598316 adf.f=f2
H -1.746567 1.250049 -0.147169 adf.f=f2
H -0.208833 2.137544 -0.147653 adf.f=f2
end
end
Task SinglePoint
Engine ADF
title final [CH3]-[CH3], etsnocv activated by etsnocv
etsnocv
ekmin 1.5
enocv 0.05
rhokmin 1.e-3
tvanalysis
end
fragments
f1 frag1.results/adf.rkf
f2 frag2.results/adf.rkf
end
fragoccupations
f1
A 5 // 4
subend
f2
A 4 // 5
subend
end
scf
converge 1E-6
end
symmetry NOSYM
xc
gga becke perdew
end
Relativity
Level None
End
EndEngine
eor
# Next densf calculations, to view the natural orbitals in this method, see
# also the the documentation for the densf analysis program and the ADF-GUI.
# Input is the adf.rkf of the molecular calculation.
$AMSBIN/densf <<eor
adffile ams.results/adf.rkf
Grid Medium
End
NOCV
Alpha
1
2
59
60
Beta
1
2
59
60
END
eor
mv TAPE41 nocv1.t41
$AMSBIN/densf <<eor
adffile ams.results/adf.rkf
Grid Medium
End
NOCV
THRESH 0.01
RESTSUM
END
eor
mv TAPE41 nocv2.t41
$AMSBIN/densf <<eor
adffile ams.results/adf.rkf
Grid Medium
End
NOCV
ALPHA
SUM 1
BETA
SUM 1
RESTSUM
END
eor
mv TAPE41 nocv3.t41
$AMSBIN/densf <<eor
adffile ams.results/adf.rkf
Grid Medium
End
NOCV
SUMBELOW 0.5
END
eor
mv TAPE41 nocv4.t41
```