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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