# [molpro-user] DFT calculations produced different energy with a different guesses

David Danovich david.danovich at gmail.com
Wed Nov 3 13:19:00 GMT 2010

```Hello,

I am calculating CuAu2 molecule in high spin state (4B2 state) using B3LYP
method. Below you can find three different possibilities I have used in the
calculations. In the first one 1) I have calculated first HF wave
function and used it as a guess for DFT calculation. Energy I got was
-468.86467917 au. In the second calculation 2) I directly have
calculated B3LYP without HF wave function. The energy I got was
-468.83995914 au. In the third calculation 3) I first have done B3LYP
calculation for state (4A2) and then used it as a guess for the calculations
of 4B2. The energy I got was
-468.85824088 au. As you can see there is quite large difference in energy
for the same state. I was trying to use different grids but it does not
solved the problem. In my opinion result should not depend on the guess so
drastically. What can be a solution for this problem?

1)

***, Peterson PP tz basis set
memory,250,m
r =   2.72684681 ang;
a = 60.65125012 degree;
geometry={Cu1;              !z-matrix geometry input
Au2,Cu1,r;
Au3,Cu1,r,Au2,a;
}
basis=cc-pVTZ-PP

{hf,maxit=500;
wf,57,3,3}

{rks,b3lyp3,maxit=500;
wf,57,3,3}

optg

Total energy  -468.86467917 au
____________________________________________________

2)
***, Peterson PP tz basis set
memory,250,m
r =   2.72684681 ang;
a = 60.65125012 degree;
geometry={Cu1;              !z-matrix geometry input
Au2,Cu1,r;
Au3,Cu1,r,Au2,a;
}
basis=cc-pVTZ-PP

{ks,b3lyp3,maxit=500;
shift,-0.1,0.0;
wf,57,3,3}

optg

Total energy -468.83995914 au

______________________________________________________

3)
***, Peterson PP tz basis set
memory,250,m
r =   2.72684681 ang;
a = 60.65125012 degree;
geometry={Cu1;              !z-matrix geometry input
Au2,Cu1,r;
Au3,Cu1,r,Au2,a;
}

! cc-pVTZ-PP

basis=cc-pVTZ-PP

{ks,b3lyp3,maxit=500;
wf,57,4,3}

{ks,b3lyp3,maxit=500;
shift,-1.0,0.0;
wf,57,3,3}

optg

Total energy -468.85824088 au
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```