[CP2K-user] [CP2K:17071] Re: Density of states with k-points in CP2K

Sam Broderick waveman68 at gmail.com
Thu Jun 2 16:04:42 UTC 2022


It's not clear to me why you are looking at the first step. Did it converge 
in just one step?

At any rate, you'll notice a difference between &DOS and &PDOS. PDOS 
returns values per orbital (s, p, d, f). If I understand it correctly, the 
density is the DOS as a solid state physicist would understand it, and 
occupation gives you a fractional filling at that energy. Not quite the 
same thing.


On Wednesday, June 1, 2022 at 7:39:20 PM UTC+2 nwi... at berkeley.edu wrote:

> Hi everyone, 
> I know that DOS and points aren't what people first think of when using 
> cp2k, but the functionality does seem to be there in some limited way... 
> Anyway, I'm wondering how to properly use it, because my test case doesn't 
> look right. I'm running a point calculation on GaAs with a 16x16x16 
> Monkhorst-Pack pack grid and then printing the total DOS. I then take the 
> columns from the DOS file (head attached) and plot energy (column 1) 
> against occupation (column 3) using the reported Fermi energy from the 
> output file of ~0.14 Ha. This results in a DOS where the Fermi energy does 
> not line up with the VBM. What's more, if I visually inspect this DOS, the 
> band gap of GaAs is >1eV. While that is closer to the experimental value, 
> the reported band gap using GGA PBE is closer to 0.3eV.  
> Questions:
> (1) What is the distinction between columns 2 and 3 in the DOS file? They 
> give similar, but not equivalent looking dos plots.
> (2) Is the Fermi energy printed in the output file the same as the Fermi 
> energy of the DOS, or is it defined different?
> I've attached my input file for reference. Thanks in advance.
>  # DOS at iteration step i = 0
>     Energy[a.u.]       Density     Occupation
>     -0.40682067         0.0009         0.0957
>     -0.40582067         0.0015         0.1543
>     -0.40482067         0.0000         0.0000
>     -0.40382067         0.0000         0.0000
>     -0.40282067         0.0034         0.3516
>     -0.40182067         0.0026         0.2656
>     -0.40082067         0.0038         0.3828
>     -0.39982067         0.0000         0.0000
> [image: Screen Shot 2022-06-01 at 10.32.10 AM.png]

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