Geometry adjust zcoord problem


Just Got Here
Hi, I'm trying to use geometry adjust and zcoord to do a PES scan which I have done before but am getting problems. This involves the approach of a solvent ligand towards a metal centre and was initially having trouble I think because they were too far part and the autoz was failing. I increased cvr_scalling from 1.3 to 2.5 to compensate based on advise in another thread and it seemed to stop crashing and is running, however, the bond I am specifying to remain constant during optimisation is most definitely not remaining of constant length... I specify 3.86 angstroms in the first step, it reduced to 3.7, in the second step (3.84 angstroms) it elongates to 7.74... where have I gone wrong in my input, I presumable have misunderstood the cvr_scaling bit as I assumed that this merely told the program how far things could be away from each other to be bonded and therefore appear in zmat...

geometry adjust
zcoord
cvr_scaling 2.5
bond 3 31 3.86 RuN constant
end
end

dft
vectors atomic
end

driver
maxiter 500
xyz 386
end

task dft optimize





Top bit of input file:

echo
start ru_pytz_dMCa_mecn_coord
charge 2

geometry
C 0.9041 -6.4201 -0.2186
C 0.7085 -4.9769 -0.1458
N 0.5549 -3.8358 -0.0884
H 0.0387 -6.8842 -0.0297
H 1.5860 -6.6992 0.4575
H 1.2218 -6.6682 -1.1338
N -0.4632 0.3302 -3.0200
N -1.3448 -0.1124 -3.9196
C -2.3038 -0.8816 -3.3460
C -1.9783 -0.9042 -2.0101
N -0.8406 -0.1460 -1.8671
N -2.4060 -1.7761 1.3763
N -3.4345 -2.4699 0.8917
C -3.5444 -2.3278 -0.4553
C -2.5104 -1.4893 -0.8002
N -1.8475 -1.1824 0.3598
C -1.1893 0.2403 -5.3309
C -4.2707 -3.2683 1.7887
N -2.6913 1.7994 1.0960
N -3.0893 3.0708 1.2034
C -2.1168 3.9247 0.8012
C -1.0694 3.1087 0.4301
N -1.4721 1.8194 0.6305
N 2.2099 2.6268 -0.7684
N 2.1964 3.9657 -0.8162
C 1.0058 4.4573 -0.3960
C 0.2656 3.3382 -0.0788
N 1.0466 2.2489 -0.3265
C -4.4284 3.3880 1.6987
C 3.3749 4.7018 -1.2708
Ru -0.0023 -0.0187 0.0591
H -3.1030 -1.3302 -3.9128
H -4.3144 -2.8187 -1.0272
H -1.0168 -0.6593 -5.9213
H -0.3296 0.9005 -5.4084
H -2.0828 0.7535 -5.6852
H -4.1814 -4.3248 1.5366
H -5.3099 -2.9516 1.7049
H -3.9148 -3.1010 2.8017
H -2.2447 4.9947 0.8128
H 0.7966 5.5139 -0.3596
H -4.3570 4.0327 2.5743
H -4.9062 2.4509 1.9716
H -5.0070 3.8836 0.9191
H 3.1113 5.3420 -2.1122
H 4.1140 3.9700 -1.5857
H 3.7770 5.3048 -0.4566
C 2.7548 -0.7918 0.7768
C 2.1371 -0.5448 2.0713
N 0.8323 -0.1594 1.9965
C 0.1632 0.0657 3.1394
C 0.7523 -0.0648 4.3895
C 2.0883 -0.4473 4.4692
C 2.7874 -0.6925 3.2934
C 3.9882 -1.2147 0.3343
N 3.8757 -1.2472 -1.0177
N 2.6618 -0.8749 -1.4224
N 1.9894 -0.5992 -0.3410
C 4.8825 -1.6479 -2.0008
H -0.8746 0.3518 3.0287
H 0.1675 0.1288 5.2802
H 2.5772 -0.5570 5.4304
H 3.8265 -0.9983 3.3219
H 4.8986 -1.4861 0.8428
H 4.4914 -1.4067 -2.9855
H 5.0674 -2.7196 -1.9282
H 5.8058 -1.0972 -1.8247
end

basis
Ru library stuttgart_rsc_1997_ecp
C library 6-311G*
N library 6-311G*
H library 6-311G*
end

ecp
Ru library stuttgart_rsc_1997_ecp
end

dft
direct
xc b3lyp
mult 3
iterations 500
end

geometry adjust
zcoord
cvr_scaling 2.5
bond 3 31 3.86 RuN constant
end
end

dft
vectors atomic
end

driver
maxiter 500
xyz 386
end

task dft optimize

geometry adjust
zcoord
cvr_scaling 2.5
bond 3 31 3.84 RuN constant
end
end

dft
vectors atomic
end

driver
maxiter 500
xyz 384
end

task dft optimize


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