[Wien] proper k-points for Nd

[Victor Zenou]

Dear Lauri
Thanks for your answer
I used only energy convergence criteria (10^-4). Still the charge
convergence was between 0.006 and 0.2 e.
The nearest neighbor distance is 6.856 a.u, I used RMT=2.7 a.u., summed to
5.4 which is much lower than 6.856. Usually large RMT is preferred to make
the calculations as fast as possible. I plan to check a phases in Al-Ti-Nd
and I chose RMT equal to 2.3, 2.5 and 2.7 respectively.
Victor



‫בתאריך יום ה׳, 17 בינו׳ 2019 ב-11:16 מאת ‪Laurence Marks‬‏ <‪
L-marks at northwestern.edu‬‏>:‬

> With such large RMT you certainly need HDLO for Nd, perhaps both d & f. I
> would not want to use such large RMTs.
>
> Have you checked that the charge convergence is good?
>
> _____
> Professor Laurence Marks
> "Research is to see what everybody else has seen, and to think what nobody
> else has thought", Albert Szent-Gyorgi
> www.numis.northwestern.edu
>
> On Thu, Jan 17, 2019, 03:04 Victor Zenou <zanov at post.bgu.ac.il wrote:
>
>> 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
>>>
>>>
>>>
>>>
>>>
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