MCSQS Query VASP

vidur · March 25, 2025, 6:17am

I am a Masters of Nuclear Engineering student at the University of New South Wales, Australia and have been using the MCSQS code to create Special Quasi-Random Structures as part of my research project.

However, I’ve been facing a few issues while using the code. As reference, I have attached (pasted at end of post as .in extension not allowed - rndstr.in) a simple sample test case with 32 atoms (distribution - 93.75% Cr and 6.25% Fe). After I create the clusters.out file using the corrdump program and run the mcsqs code using:

mcsqs -n=32 (no of atoms?) I get the following error: Impossible to match point correlations due to incompatible supercell size.

The code however works when I choose to run it with 50-50 distribution.

My understanding of the code is that it should work as long at the distribution percentages (93.75 and 6.25% above), produce whole integers considering the no of atoms.

Any help regarding this would be highly appreciated.

Thanks and regards,
Vidur Tuli

5.44 5.44 4.15 90 90 120
2 0 0
0 2 0
0 0 2
0.000000000000000 0.000000000000000 0.000000000000000 Cr=0.9375,Fe=0.0625
0.000000000000000 0.000000000000000 0.500000000000000 Cr=0.9375,Fe=0.0625
0.500000000000000 0.500000000000000 0.000000000000000 Cr=0.9375,Fe=0.0625
0.500000000000000 0.000000000000000 0.000000000000000 Cr=0.9375,Fe=0.0625
0.000000000000000 0.500000000000000 0.000000000000000 Cr=0.9375,Fe=0.0625
0.500000000000000 0.500000000000000 0.500000000000000 Cr=0.9375,Fe=0.0625
0.500000000000000 0.000000000000000 0.500000000000000 Cr=0.9375,Fe=0.0625
0.000000000000000 0.500000000000000 0.500000000000000 Cr=0.9375,Fe=0.0625
0.409800000000000 0.319600000000000 0.250000000000000 Cr=0.9375,Fe=0.0625
0.319600000000000 0.409800000000000 0.750000000000000 Cr=0.9375,Fe=0.0625
0.090200000000000 0.180400000000000 0.750000000000000 Cr=0.9375,Fe=0.0625
0.090200000000000 0.409800000000000 0.750000000000000 Cr=0.9375,Fe=0.0625
0.180400000000000 0.090200000000000 0.250000000000000 Cr=0.9375,Fe=0.0625
0.409800000000000 0.090200000000000 0.250000000000000 Cr=0.9375,Fe=0.0625
0.909800000000000 0.819600000000000 0.250000000000000 Cr=0.9375,Fe=0.0625
0.909800000000000 0.319600000000000 0.250000000000000 Cr=0.9375,Fe=0.0625
0.409800000000000 0.819600000000000 0.250000000000000 Cr=0.9375,Fe=0.0625
0.819600000000000 0.909800000000000 0.750000000000000 Cr=0.9375,Fe=0.0625
0.819600000000000 0.409800000000000 0.750000000000000 Cr=0.9375,Fe=0.0625
0.319600000000000 0.909800000000000 0.750000000000000 Cr=0.9375,Fe=0.0625
0.590200000000000 0.680400000000000 0.750000000000000 Cr=0.9375,Fe=0.0625
0.590200000000000 0.180400000000000 0.750000000000000 Cr=0.9375,Fe=0.0625
0.090200000000000 0.680400000000000 0.750000000000000 Cr=0.9375,Fe=0.0625
0.590200000000000 0.909800000000000 0.750000000000000 Cr=0.9375,Fe=0.0625
0.590200000000000 0.409800000000000 0.750000000000000 Cr=0.9375,Fe=0.0625
0.090200000000000 0.909800000000000 0.750000000000000 Cr=0.9375,Fe=0.0625
0.680400000000000 0.590200000000000 0.250000000000000 Cr=0.9375,Fe=0.0625
0.680400000000000 0.090200000000000 0.250000000000000 Cr=0.9375,Fe=0.0625
0.180400000000000 0.590200000000000 0.250000000000000 Cr=0.9375,Fe=0.0625
0.909800000000000 0.590200000000000 0.250000000000000 Cr=0.9375,Fe=0.0625
0.909800000000000 0.090200000000000 0.250000000000000 Cr=0.9375,Fe=0.0625
0.409800000000000 0.590200000000000 0.250000000000000 Cr=0.9375,Fe=0.0625

avdw · March 25, 2025, 4:36pm

I believe your cell should be
1 0 0
0 1 0
0 0 1
instead of
2 0 0
0 2 0
0 0 2
since your coordinates are clearly in fractions <1.

The next problem is that the constraint composition*(nb of atom in a sublattice)=integer is not satisfied. It is not in general enough to have composition*(total nb of atom)=integer, because the point correlation for each sublattice must match the specified constraint.
In your case, your smallest sublattice has only 8 atoms, as you can see with:

corrdump.exe -2=0.01 -clus -noe -ro -l=rndstr.in  ; getclus

So your supercell has to be much bigger to match the correlation on the 8-atom sublattice.

BTW, you don’t need your rndstr.in to be so big. A smaller cell exists, see:

cellcvrt.exe -s < rndstr.in

You can set the supercell size with the -n option of mcsqs,e.g.:

mcsqs -n=32

vidur · March 25, 2025, 4:43pm

Dear Professor Van De Walle,

Thanks for your quick reply! I seem to have gotten over my initial hurdle. Your explanation was of great help.

Regards,
Vidur

chx · March 26, 2025, 7:15pm

Dear Professor Van De Walle,
I am trying to use the mcsqs to creat a 2D monolayer alloy configuration. Now, I have a confusion about the Code usage part in your paper (CALPHAD: Computer Coupling of Phase Diagrams and Thermochemistry 42 (2013) 13-18). That is "3. Finally, the positions Xi of the crystallographic sites (expressed in the same coordinate system as the lattice vectors) are given, …Note that the concentrations must sum up to 1 for each site." I am not sure whether the Xi infer to the position of crystallographic site or one atom position. Because in the example part of this paper, the table 2 seem to give the position of all atoms.If it is an atom position, I think it should not have different composition in one atom position. Is it Right?( Please forgive me low-level understanding, I just have a confusion)
And I also found the expression "Finally, atom positions and types are given, expressed in the same coordinate system" in the website manual. So, I just would like to know what does the real mean for Xi. Could you give me an explanation? Thanks a lot in advance.

Best Regards
HX Cheng

avdw · March 26, 2025, 7:44pm

Sorry - I just interchangeably used the term "sites" and "atoms". To me it’s the same.

oridon33 · March 30, 2025, 11:42pm

Hello everyone,
I have a similar problem. after following the instructions. the total atoms is 128 for BCC structure.
My rndstr.in is as follows:.
13.28 13.28 13.28 90 90 90
1 0 0
0 1 0
0 0 1
0.000000 0.000000 0.000000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.000000 0.000000 0.250000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.000000 0.000000 0.500000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.000000 0.000000 0.750000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.000000 0.250000 0.000000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.000000 0.250000 0.250000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.000000 0.250000 0.500000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.000000 0.250000 0.750000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.000000 0.500000 0.000000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.000000 0.500000 0.250000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.000000 0.500000 0.500000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.000000 0.500000 0.750000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.000000 0.750000 0.000000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.000000 0.750000 0.250000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.000000 0.750000 0.500000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.000000 0.750000 0.750000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.250000 0.000000 0.000000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.250000 0.000000 0.250000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.250000 0.000000 0.500000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.250000 0.000000 0.750000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.250000 0.250000 0.000000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.250000 0.250000 0.250000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.250000 0.250000 0.500000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.250000 0.250000 0.750000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.250000 0.500000 0.000000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.250000 0.500000 0.250000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.250000 0.500000 0.500000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.250000 0.500000 0.750000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.250000 0.750000 0.000000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.250000 0.750000 0.250000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.250000 0.750000 0.500000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.250000 0.750000 0.750000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.500000 0.000000 0.000000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.500000 0.000000 0.250000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.500000 0.000000 0.500000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.500000 0.000000 0.750000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.500000 0.250000 0.000000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.500000 0.250000 0.250000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.500000 0.250000 0.500000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.500000 0.250000 0.750000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.500000 0.500000 0.000000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.500000 0.500000 0.250000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.500000 0.500000 0.500000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.500000 0.500000 0.750000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.500000 0.750000 0.000000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.500000 0.750000 0.250000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.500000 0.750000 0.500000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.500000 0.750000 0.750000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.750000 0.000000 0.000000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.750000 0.000000 0.250000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.750000 0.000000 0.500000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.750000 0.000000 0.750000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.750000 0.250000 0.000000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.750000 0.250000 0.250000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.750000 0.250000 0.500000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.750000 0.250000 0.750000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.750000 0.500000 0.000000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.750000 0.500000 0.250000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.750000 0.500000 0.500000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.750000 0.500000 0.750000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.750000 0.750000 0.000000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.750000 0.750000 0.250000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.750000 0.750000 0.500000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.750000 0.750000 0.750000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.125000 0.125000 0.125000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.125000 0.125000 0.375000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.125000 0.125000 0.625000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.125000 0.125000 0.875000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.125000 0.375000 0.125000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.125000 0.375000 0.375000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.125000 0.375000 0.625000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.125000 0.375000 0.875000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.125000 0.625000 0.125000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.125000 0.625000 0.375000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.125000 0.625000 0.625000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.125000 0.625000 0.875000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.125000 0.875000 0.125000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.125000 0.875000 0.375000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.125000 0.875000 0.625000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.125000 0.875000 0.875000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.375000 0.125000 0.125000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.375000 0.125000 0.375000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.375000 0.125000 0.625000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.375000 0.125000 0.875000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.375000 0.375000 0.125000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.375000 0.375000 0.375000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.375000 0.375000 0.625000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.375000 0.375000 0.875000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.375000 0.625000 0.125000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.375000 0.625000 0.375000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.375000 0.625000 0.625000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.375000 0.625000 0.875000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.375000 0.875000 0.125000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.375000 0.875000 0.375000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.375000 0.875000 0.625000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.375000 0.875000 0.875000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.625000 0.125000 0.125000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.625000 0.125000 0.375000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.625000 0.125000 0.625000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.625000 0.125000 0.875000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.625000 0.375000 0.125000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.625000 0.375000 0.375000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.625000 0.375000 0.625000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.625000 0.375000 0.875000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.625000 0.625000 0.125000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.625000 0.625000 0.375000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.625000 0.625000 0.625000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.625000 0.625000 0.875000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.625000 0.875000 0.125000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.625000 0.875000 0.375000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.625000 0.875000 0.625000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.625000 0.875000 0.875000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.875000 0.125000 0.125000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.875000 0.125000 0.375000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.875000 0.125000 0.625000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.875000 0.125000 0.875000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.875000 0.375000 0.125000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.875000 0.375000 0.375000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.875000 0.375000 0.625000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.875000 0.375000 0.875000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.875000 0.625000 0.125000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.875000 0.625000 0.375000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.875000 0.625000 0.625000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.875000 0.625000 0.875000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.875000 0.875000 0.125000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.875000 0.875000 0.375000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.875000 0.875000 0.625000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195
0.875000 0.875000 0.875000 Nb=0.203,Ni=0.203,Ti=0.203,Zr=0.195,Co=0.195

The errors I am getting are as follows:
It is impossible to match point correlations due to incompatible supercell sizes.

using corrdump -l=rndstr.in -ro -noe -nop -2=0.01