[Wien] proper k-points for Nd

[Victor Zenou]

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
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