[Pw_forum] XDM stress dependent on k-point parallelization?

[Alberto Otero de la Roza]

Hi Malte,

Yes, sorry, there is a bug in the XDM code related to the
parallelization. All XDM quantities are correct with the default
number of pools (i.e. mpirun -n x pw.x), so I recommend not using this
for now. I'll try to get it fixed soon and let the forum know when
it's done.

Best,

Alberto

---
Dr. Alberto Otero de la Roza
Department of Chemistry, 
University of British Columbia, Okanagan
Kelowna, British Columbia, Canada V1V 1V7


* Malte Sachs <malte.sachs at chemie.uni-marburg.de> [2017-08-01 15:08:58 +0200]:
> Dear all,
> 
> I have tried to perform vc-relax calculations with Quantum Espresso v6.0
> using the XDM Van-der-Waals correction. I get some strange results, because
> it seems that the calculated XDM stress depends on the k-point
> parallelization. As a test I performed three scf calculations using the same
> input (see attached) just variing the number of k-point pools:
> 
> 2 pools with 3 k-points: XDM stress (-33.37 -33.37 -40.79)
> 
> 3 pools with 2 k-points: XDM stress (-58.75 -58.75 -61.19)
> 
> 6 pools with 1 k-point: XDM stress (-117.51 -117.51 -122.37)
> 
> The stress ratio 1: 1/2 : 1/3 is the inverse of the k-point ratio per
> pool... Has somebody seen something like this before?
> 
> Best regards,
> 
> Malte
> 
> -- 
> Malte Sachs
> Anorganische Chemie, Fluorchemie
> Philipps-Universität Marburg
> Hans-Meerwein-Straße 4
> 35032 Marburg (Paketpost: 35043 Marburg)
> Tel.: +49 (0)6421 28 - 25 39 5
> http://www.uni-marburg.de/fb15/ag-kraus/
> 

> &CONTROL
>     calculation = 'scf',
>     title = 'UCl6_P-3m1'
>     verbosity = 'high'
>     prefix = 'UCl6_P3'
>     outdir = './outdir/'
>     pseudo_dir = '/home/Sachsm/Promotion/Pseudos/'
>     tstress = .true.,
>     wf_collect = .true.
>     etot_conv_thr = 1.0D-8,
>     forc_conv_thr = 1.0D-6
>  /
> &SYSTEM
>     ibrav = 4,
>     celldm(1) = 20.55532424,
>     celldm(3) = 0.461663392,
>     nat =  21,
>     ntyp = 2,
>     nbnd = 90,
>     occupations = 'fixed',
>     ecutwfc = 100,
>     ecutrho = 800,
>     vdw_corr = 'xdm',
>     xdm_a1 = 0.6512,
>     xdm_a2 = 1.4633,
>  /
>  &ELECTRONS
>     mixing_beta = 0.4,
>     mixing_mode = 'plain',
>     conv_thr = 1.D-10,
>  /
> &IONS
>  /
>  &CELL
>  /
> 
> K_POINTS (automatic)
>   2 2 4 0 0 0
> 





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