[Q-e-developers] QE 6.1 vs. 6.2 performance; Possible starting_charge issue

[Andrii Shyichuk]

Dear QE developers,

My name is Andrii Shyichuk, I am an adjunct professor at University of 
Wrocław, Poland.

I am trying to run some calculations on lutetium oxide with QE 6.1 as 
well as QE 6.2.
Please consider the two groups of input and output files, LO2f_61 and 
LO2f_62. The input files are identical, and the resulting grids reported 
in the in the output files, are identical too.
However, QE 6.2 requests ~8.5 Gb memory, while QE 6.1 requests only 
~3.5.
SCF steps last longer in QE 6.2, and if I specify starting_charge, the 
number of steps increases from 9 to 23.

Both codes run on the same supercomputer, were compiled with the same 
libraries and compilers, and both run in MPI+openMP setup, 1 node, 8 
cores.

There is another potential issue I'd like to report.
In the cell of 32 Lu and 48 O, starting charge is calculated as 544 ( = 
32*8 (Lu3+) + 48*6 (O zero) ), and renormalized to 640 (Lu3+, O2-). In 
QE 6.2, starting_charge can be specified (and is read correctly, 
according to the output file), but that results in starting total charge 
of 570 (LO2fc_62), which is renormalized to 640. This is not a problem 
as is - given the renormalization, but might indicate some problem in 
the routines related to starting_charge keyword.

Also, my Lu2O3 calculation shows large negative rho (~3), compared to 
640 electrons in the system, which does not go away at the end of SCF 
cycle, and is not affected by PW cutoff up to 100 Ry and charge density 
cutoff up to 1000 Ry. SCF if achieved anyway.
Should I ignore this issue?

The Lu potential (neither published nor tested) was obtained from Kevin 
Garrity, but I trust him on this one and will do some testing.

Thank you in advance for your comments.
Best regards.
Andrii



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