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which torsions must be removed in RSURFACE?

Bernhard Dick
bernhard.dick@chemie.uni-regensburg.de

I want to study the potential surface along a torsional motion, as an example I take biphenyl. With Chemcraft I create the coordinates below. The torsion is the dihedral 6-10-12-13. When I want to keep C2 symmetry, the angle 7-10-12-14 is equivalent, but also the dihedrals 6-10-12-14 and 7-10-12-15 are fixed once 6-10-12-13 is set. Should I remove all three torsions by IRZMAT, or only one of each symmetry-related pair, or none at all? I got funny results when I removed all three (i.e. oscillating energies along the PES), and non-convergence of geometry when I remove only one. Is there perhaps a principal problem in combining RSURFACE+DLC with symmetry?

best regards,
Bernhard


$DATA
biphenyl - all atoms
Cn        2

CARBON      6.0      0.000000000         0.000000000        -3.572765781
CARBON      6.0     -0.916166015         0.789265422        -2.874601781
CARBON      6.0      0.916166015        -0.789265422        -2.874601781
HYDROGEN    1.0     -1.628946079         1.403316421        -3.417774781
HYDROGEN    1.0      1.628946079        -1.403316421        -3.417774781
CARBON      6.0     -0.916166015         0.789265422        -1.478271781
CARBON      6.0      0.916166015        -0.789265422        -1.478271781
HYDROGEN    1.0     -1.628946079         1.403316421        -0.935098781
HYDROGEN    1.0      1.628946079        -1.403316421        -0.935098781
CARBON      6.0      0.000000000         0.000000000        -0.780107781
HYDROGEN    1.0      0.000000000         0.000000000        -4.659112781
CARBON      6.0      0.000000000         0.000000000         0.759892219
CARBON      6.0     -1.183991666         0.224669712         1.482400783
CARBON      6.0      1.183991666        -0.224669712         1.482400783
CARBON      6.0     -1.184309844         0.224730088         2.876252941
CARBON      6.0      1.184309844        -0.224730088         2.876252941
CARBON      6.0      0.000000000         0.000000000         3.579900516
HYDROGEN    1.0     -2.110672046         0.400513022         0.944993107
HYDROGEN    1.0      2.110672046        -0.400513022         0.944993107
HYDROGEN    1.0     -2.111861534         0.400738735         3.413538617
HYDROGEN    1.0      2.111861534        -0.400738735         3.413538617
HYDROGEN    1.0      0.000000000         0.000000000         4.665900861
$END

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