Geometry optimization with DFT-D3


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Hello everyone,

I ran into trouble doing geometry optimizations using D3-vdW corrections.

Examplary case: deprotonated Thymine

geometry noautoz noautosym
N       28.244018096  33.246369348  11.861178719
C       26.957713719  33.685034935  11.926387900
H       26.823102260  34.757893956  11.867853974
C       25.930007044  32.837449783  12.064908038
C       24.513432935  33.276081116  12.167416770
H       24.425223267  34.360732076  12.102674481
H       23.909994128  32.821313542  11.381993139
H       24.078438912  32.937259852  13.107471042
C       26.234367695  31.397900833  12.147964689
O       25.298061166  30.602638634  12.306878919
N       27.525290642  30.994407595  12.048677282
C       28.536759287  31.851707150  11.897827184
O       29.728553304  31.547621191  11.786332588
C       29.336853247  34.156507367  11.653137720
H       30.142174569  33.932485013  12.347562797
H       28.984684813  35.174718687  11.805840101
H       29.744704919  34.063888929  10.645354658
end

charge -1
scratch_dir temp
start

basis
 C library Def2-SVP
 O library Def2-SVP
 N library Def2-SVP
 H library Def2-SVP
end

memory 5000 mb

dft
 xc xpbe96 cpbe96
 disp vdw 3
 direct
 iterations 1000
 noprint "final vectors analysis"
end

task dft optimize



It does not crash as such but it just creates totally weird geometries that destroy the molecule. I noticed that already in the first electronic SCF, the estimated vdW Energies are very large.

    Dispersion correction =       -1.517049126987


I did a comparative run with Turbomole and there it is ~-0.02 and also the optimization finishes without problem.

Anything obvious I should change?

Cheers
B