[CP2K-user] Converging b3lyp/6-311++G**

Kristjan Eimre kristj... at gmail.com
Mon Oct 1 15:41:08 UTC 2018

Dear CP2K community,

I am having trouble converging the SCF of a b3lyp/6-311++G** calculation 
for a fairly small molecule consisting of C and H.

Without too much trouble, I was able to converge the b3lyp/6-311++G** for 
benzene and also b3lyp/6-311G** for my molecule (so without the diffuse 
basis functions).

I optimized the geometries also with b3lyp/6-311G**.

Additionally, for my molecule, I converged blyp/6-311++G**, which I was 
using as the initial guess to b3lyp calculation.

I attached one of the inputs scripts that I tried and the corresponding 

Here are the different things that I tried:
* Played with the parameters in QS (most notably EPSFIT, ALPHA0_H)
* OT with CG minimizer
* Diagonalization
* MT poisson solver
* UKS calculation
* smaller basis set, 6-311+G* (from EMSL)

But unfortunately everything failed.

Which knobs should I turn to possibly reach convergence? Any hints are very 
much appreciated.

best regards,
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