[Wien] proper k-points for Nd

[Victor Zenou]

Hi
Here is updated question:

Dear Wien2k users

I'm using wien2k version 17.1 installed on Ubunto 18.04.

I need to calculate the enthalpy of formation of few intermetallic phases
that include Nd. For that element I used RMT=2.7 a.u. and RMT*Kmax=8.5
for spin-polarization
calculations via GGA-PBE. I didn't try spin-orbit coupling. Yet.

The first stage is to choose proper k-points, which will give accurate
results (I used 1x10^-4 Ryd for energy convergence) on one hand, but on the
other hand won't be expensive in terms of computing time.

I noticed that there are large energy fluctuations (1x10^-2 Ryd; which are
2 order of magnitude higher than the energy accuracy (defined by
convergence criterion), even when I went to 15,000 k-points. Here is a list
of energy as function of k-points:

K-points          IBZ      E [Ryd]

 100       8        -77040.4692

 500     38        -77040.4780

1000    81        -77040.5062

2000    120      -77040.5061

3000    208      -77040.4391

4000    244      -77040.4699

5000    280      -77040.4878

7500    455      -77040.4707

10000  540      -77040.4881

15000  840      -77040.4694



I would be happy to get an idea what could have gone wrong.

Best regards, Victor


‫בתאריך יום ד׳, 16 בינו׳ 2019 ב-13:59 מאת ‪Victor Zenou‬‏ <‪
zanov at post.bgu.ac.il‬‏>:‬

> Dear Wien2k users
>
> I'm using wien2k version 17.1 installed on Ubunto 18.04.
>
> As a part of investigation of intermetallic phases in Al-Ti-Nd system, I
> need to calculate the enthalpy of formation of few phases in that system.
> For that purpose, I start calculating enthalpy (equal to energy at 0K) for
> each element and phase at their optimal relaxed state.  I used
> spin-polarization calculations. (GGA-PBE) As advised in Wien2k website I
> used the same RMT for each elements: 2.3, 2.5 and 2.7 a.u. for Al, Ti and
> Nd, respectively. Also proper RMT*Kmax (7.5 to Ti, 8.5 to Nd and 7.0 for
> the rest).
>
> The first stage is to choose proper k-points, which give you accurate
> results (I used 1x10^-4 Ryd for energy convergence) on one hand, but also
> some save computing time.
>
> The calculation for all elements and phases went OK, but Nd. From certain
> k-points the energy fluctuated between 2 values (differed by 1x10^-2).
> Attach a list of energy as function of k-points:
>
> K-points          IBZ      E [Ryd]
>
>  100       8        -77040.4692
>
>  500     38        -77040.4780
>
> 1000    81        -77040.5062
>
> 2000    120      -77040.5061
>
> 3000    208      -77040.4391
>
> 4000    244      -77040.4699
>
> 5000    280      -77040.4878
>
> 7500    455      -77040.4707
>
> 10000  540      -77040.4881
>
> 15000  840      -77040.4694
>
>
>
> I tried to get smart and did volume optimization using 4000 k-points,
> later 5000 k-points. I got strange results.
>
> I would be happy to get an idea what could have gone wrong.
>
> I didn't try spin-orbit coupling
>
> Best regards, Victor
>
>
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20190117/bb8a3187/attachment.html>