[CP2K-user] nonscc dftb problem

Xin Wu ichb... at gmail.com
Mon Sep 16 07:52:45 UTC 2019


On Sunday, September 15, 2019 at 11:49:57 AM UTC+2, simin pahlavi wrote:
> 1) If my input is set up correctly for these type of calculation.

No. There are several errors in the FORCE_EVAL section:

1. MGRID is only relevant to DFT, but not NONSCC-DFTB (please see the DFT 
section in the CP2K manual).

2. You have an open QS section, please &END QS.

3. In the POISSON section, you are requesting periodic boundary conditions. 

4. There may be some other errors in your input file.

> 2) Normally what the range of cuttof in nonscc dftb should be?

Normally there is no cutoff in DFTB.

> 3) how should I decide on type of mixing , based on convergence speed up 
> only?

You're using NONSCC-DFTB. As the name has already implied, there is no SCF 
iteration at all.

The MIXING approach is only for the SCF procedure. It generates new density 
matrix by mixing the electron density in the current iteration with that 
from the preceding SCF iteration, so that the variation of electron density 
during the SCF procedure becomes smooth and therefore it leads accelerated 
convergence. The default values are robust enough for most of applications. 
Hence, it's better to use these default settings.

> Thanks in advance,

You're welcome!

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