C2H2: Localization of Molecular Orbitals
Sample directory: adf/Cntrs.LocOrb_C2H2/
An illustration of the computation of localized molecular orbitals in C2H2.
The delocalized molecular orbitals as they result from the scf are localized in two different ways. In the first the three σ bonds are recombined only among themselves (no π bonds are mixed in), yielding two equivalent localized CH σ bonds and one localized σ bond. In a second step the localization of the remaining bond (the two π's) is performed, but this produces nothing new since no combination of the two π's is more localized then they are already by themselves.
$ADFBIN/adf << eor title C2H2, localization Sigma and Pi separately Atoms C 0 0 .63 C 0 0 -.63 H 0 0 1.63 H 0 0 -1.63 END Basis Type TZP Core Small End LocOrb alfa 4 5 alfa 1 2 3 END integration 4.0 end input eor
In the first localization cycle the π-orbitals are left out: #4 and #5 in the list of all occupied valence MOs: first 3 MOs of the first irreducible representation (s), then the 2 from the second irrep (π). In the second localization step the first three (meanwhile localized) orbitals are kept aside.
With densf the local orbitals can be computed in a user-defined grid (for plotting purposes). densf requires a file with name TAPE21.
$ADFBIN/densf << eor Grid 0. -5. -5. 100 100 0. 0. 1. 10. 0. 1. 0. 10. End Orbitals Local 1 2 3 4 5 End END INPUT eor
The program cntrs is applied to process the densf result file TAPE41.
$ADFBIN/cntrs << eor SCAN 0.01 0.02 0.04 0.08 0.16 0.32 0.64 1.28 -0.01 -0.02 -0.04 -0.08 -0.16 -0.32 -0.64 -1.28 END file ctr.a1 LocOrb%1 1.00 file ctr.a2 LocOrb%2 1.00 file ctr.a3 LocOrb%3 1.00 file ctr.a4 LocOrb%4 1.00 file ctr.a5 LocOrb%5 1.00 END INPUT eor
Again, gnuplot may be used to display the result on your screen.
$gnuplot << eor set term dumb 100 80 set output "outplot" plot "ctr.a1" using 1:2 with lines plot "ctr.a2" using 1:2 with lines plot "ctr.a3" using 1:2 with lines plot "ctr.a4" using 1:2 with lines plot "ctr.a5" using 1:2 with lines eor cat outplot
This results in 5 pictures, the first one looking like:
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The second illustration of the computation of localized molecular orbitals in C2H2 combines directly all MOs (σ and π). This yields 3 equivalent 'banana' bonds, mixtures of σ and π, and two equivalent pure σ bonds.
$ADFBIN/adf << eor title C2H2 localization without frozen orbitals Atoms C 0 0 .63 C 0 0 -.63 H 0 0 1.63 H 0 0 -1.63 end fragments C t21.C H t21.H end integration 4.0 locorb end end input eor
