Optimization of H2O

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Optimization of H2O was performed at four level without error.
1) HF/6-31g
2) HF/6-31g**
3) B3LYP/6-31g
4) B3LYP/6-31g**

However, the O-H bond length of the optimized structures was approx. 1.8 angstrom for level 1)-4).
Up to my limited knowledge, the O-H bond length of H2O should be 0.9 - 1 angstrom.

The below are the input file of level 1)-4).

1) HF/6-31g

start h2ohf631eg
title "Optimization of water in HF/6-31g basis set"

permanent_dir /home/hong/mutant/scratch
scratch_dir /home/hong/mutant/scratch

geometry units au
O 0.00000000 0.00000000 0.00000000
H 0.00000000 1.43042809 -1.10715266
H 0.00000000 -1.43042809 -1.10715266
end
basis
* library 6-31g
end

task scf optimize

2) HF/6-31g**

start h2ohf631stareg
title "Optimization of water in HF/6-31g** basis set"

permanent_dir /home/hong/mutant/scratch
scratch_dir /home/hong/mutant/scratch

geometry units au
O 0.00000000 0.00000000 0.00000000
H 0.00000000 1.43042809 -1.10715266
H 0.00000000 -1.43042809 -1.10715266
end

basis
* library 6-31g**
end

driver
maxiter 1000
end

task scf optimize

3) B3LYP/6-31g

start h2odft631eg
title "Optimization of water in B3LYP/6-31g basis set"

permanent_dir /home/hong/mutant/scratch
scratch_dir /home/hong/mutant/scratch

geometry units au
O 0.00000000 0.00000000 0.00000000
H 0.00000000 1.43042809 -1.10715266
H 0.00000000 -1.43042809 -1.10715266
end
basis
* library 6-31g
end

dft
xc b3lyp
end

task dft optimize

4) B3LYP/6-31g**

start h2odft631stareg
title "Optimization of water in B3LYP/6-31g** basis set"

permanent_dir /home/hong/mutant/scratch
scratch_dir /home/hong/mutant/scratch

geometry units au
O 0.00000000 0.00000000 0.00000000
H 0.00000000 1.43042809 -1.10715266
H 0.00000000 -1.43042809 -1.10715266
end
basis
* library 6-31g**
end

dft
xc b3lyp
end

task dft optimize

What is the reason to cause the calculated O-H bond length longer than the general O-H bond length??

Thank you!

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Threads 57
Posts 278



Units are Angstrom for bonds and degrees for angles

     Type          Name      I     J     K     L     M      Value       Change
----------- -------- ----- ----- ----- ----- ----- ---------- ----------
1 Stretch 1 2 0.97586 0.01866
2 Stretch 1 3 0.97586 0.01866
3 Bend 2 1 3 108.30143 3.78124

==============================================================================
You can see the bond lengths in terms of Angstrom.

 internuclear distances
------------------------------------------------------------------------------
center one | center two | atomic units | a.u.
------------------------------------------------------------------------------
2 H | 1 O | 1.84411 | 1.84411
3 H | 1 O | 1.84411 | 1.84411
------------------------------------------------------------------------------
number of included internuclear distances: 2
==============================================================================
Those are expressed by a.u.
Edited On 8:05:12 AM PDT - Tue, Jul 23rd 2019 by Xiongyan21

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Threads 6
Posts 18
What a silly mistake!
I just visualize the output file by "Avogadro" without reading the output file.

Thank you!


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