Hello all,

this is me back again, this time with another question. I am running a geometry optimisation on a small model compound using G09 D.01 in combination with NBO6. I have generated a z-matrix in Chemcraft (alternatively Molden) and specified which pair of orbitals I want deleted using the $DEL section. There is virtually no change in the geometry during the optimisation run (it's static), which seems not reasonable to me. Deletion of this particular pair of orbitals should result in a significant change of the structure. I believe this is rather a "technical" problem, and I was hoping for a potential cause and solution to the problem from the forum. See my input for this calculation below. I want to add that I run the test calculation on difluoroethene from the tutorial plus some tests on an even smaller model of the molecule I am actually interested in - in both cases the calculation seemed to have worked.

Thanks for your advice.

Tobias

#P opt(z-matrix,tight) m062x/def2svp pop=(nbo6del) int=ultrafine

PBC2CO final material (xray)

0 1

P

C 1 R12

C 1 R13 2 A213

C 1 R14 2 A214 3 D3214

O 2 R25 1 A125 3 -D3125

B 2 R26 1 A126 3 D3126

C 3 R37 1 A137 2 -D2137

C 3 R38 1 A138 2 D2138

H 4 R49 1 A149 2 -D2149

H 4 R4_10 1 A14_10 2 D214_10

H 4 R4_11 1 A14_11 2 D214_11

N 6 R6_12 2 A26_12 1 D126_12

H 12 R12_13 6 A6_12_13 2 D26_12_13

H 12 R12_14 6 A6_12_14 2 -D26_12_14

H 7 R7_15 3 A37_15 1 -D137_15

H 8 R8_16 3 A38_16 1 -D138_16

H 8 R8_17 3 A38_17 1 D138_17

H 8 R8_18 3 A38_18 1 D138_18

Variables:

R12 = 1.89574722

R13 = 1.85190289

A213 = 89.36726703

R14 = 1.85950795

A214 = 98.55735519

D3214 = 103.26628333

R25 = 1.20550525

A125 = 124.56408577

D3125 = 160.73340099

R26 = 1.61904018

A126 = 107.99179994

D3126 = 16.17038466

R37 = 1.35601533

A137 = 116.85079807

D2137 = 15.15126100

R38 = 1.49842363

A138 = 118.09138994

D2138 = 168.95657239

R49 = 1.09875338

A149 = 112.37047812

D2149 = 58.04999054

R4_10 = 1.09973323

A14_10 = 106.15373752

D214_10 = 60.82322427

R4_11 = 1.09780279

A14_11 = 110.94354935

D214_11 = 178.44996515

R6_12 = 1.38671764

A26_12 = 119.81818843

D126_12 = 166.22788442

R12_13 = 1.01440265

A6_12_13 = 120.09046077

D26_12_13 = 1.89195724

R12_14 = 1.01144248

A6_12_14 = 125.13579593

D26_12_14 = 179.91460432

R7_15 = 1.09608369

A37_15 = 118.75251780

D137_15 = 174.14876695

R8_16 = 1.10219191

A38_16 = 110.42516239

D138_16 = 61.30402473

R8_17 = 1.10110751

A38_17 = 110.56101227

D138_17 = 56.48289816

R8_18 = 1.09868651

A38_18 = 111.53945990

D138_18 = 177.95216432

$NBO $END

$DEL delete 2 orbitals 16 38 $END