From NWChem
Viewed 1178 times, With a total of 2 Posts
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| 5:29:27 PM PST - Thu, Nov 6th 2014 |
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Hello
Just for a test run on H atomic energy. I was doing a "task dft energy" calculation with and without noscf tag in dft block. I obtained energies differing by 4e^-4 H=0.01 eV (not bad). I know doing such a calculation doesn't make sense but still I wanted to confirm that non self consistent cycles would give the same energies which is not the case.
Input file:
echo
title "cluster"
geometry autosym
H 20.995999999999999 13.741000000000000 13.047000000000001
end
basis "ao basis" cartesian
H library 6-311G**
end
dft
iterations 3000
direct
mult 2
XC xpbe96 cpbe96
convergence ncyds 3000
noscf
end
DRIVER
XYZ a.xyz
MAXITER 500
END
task dft energy
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Edoapra Forum:Admin, Forum:Mod, bureaucrat, sysop
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Forum Vet
Threads 7
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| 5:56:27 PM PST - Thu, Nov 6th 2014 |
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Since the starting guess is the HF wavefunction, the two energies have to be different since you choose the PBE functional.
If you use "xc hfexch" (a.k.a. HF exchange) in your input files, the energies must be the same.
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| 9:36:26 PM PST - Fri, Nov 7th 2014 |
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Thank you. That makes sense.
So for an atom having noscf tag gave me the energy right away (without scf loop) however not having noscf went through 4 scf loops before printing the final energy. So if I run a bigger molecule it should do an electronic minimization (scf loops), right (irrespective of noscf's presence)? **confused**
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