[CP2K-user] [CP2K:16825] Re: xTB descrepancy between CP2K and DFTB+

[Xavier Bidault]

Hello,

I just posted also on DFTB+ issues 
(https://github.com/dftbplus/dftbplus/issues/1001), including the input 
script for DFTB+

Xavier

On Tuesday, April 5, 2022 at 3:22:02 PM UTC-5 Xavier Bidault wrote:

> Hello,
>
> I run a variable-cell optimization of a high-energy molecular crystal, 
> beta-HMX, with CP2K 9.1 and DFTB+ 21.2, both using GFN1-xTB, which includes 
> D3(BJ) correction. To compare apples to apples, I optimized the same 
> supercell, using the Gamma point. The initial (experimental) volume for the 
> supercell is 2069.80 A3. The resulting volume is:
> 1950.83 A3 with DFTB+
> 1759.92 A3 with CP2K
>
> In order to check if I did something wrong in the configuration files, I 
> used DFTB + D3(0) with the default DFTB parameter file from CP2K for both 
> CP2K and DFTB+, and I find:
> 1467.79 A3 with DFTB+
> 1467.14 A3 with CP2K
> So, DFTB + D3(0) is consistent between CP2K and DFTB+, but not GFN1-xTB.
>
> IMO, the dispersion correction of xTB is wrong somewhere in CP2K. Looking 
> at the difference between CP2K and DFTB+, could it be that D3(BJ) 
> correction is counted twice in CP2K? Or with some wrong units we don't have 
> access to?
>
> I attached the CP2K input file for the GFN1-xTB calculation.
>
> Please, let me know.
>
> Thank you,
> Xavier
>
>
>

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