Could not map configurations

[sjtuzhanglei]

Dear CASM developers,

The configs were completed with calculations, with energy values. Surprisingly, I cannot do casm update:

May I know why??

casm update -- Read: Settings -- { "force" : false, "mapping" : { "cost_tol" : 0.000010000000, "fix_lattice" : false, "fix_volume" : false, "ideal" : false, "k_best" : 1, "lattice_weight" : 0.500000000000, "max_va_frac" : 0.500000000000, "max_vol_change" : 0.300000000000, "min_va_frac" : 0.000000000000, "primitive_only" : false, "robust" : false, "strict" : false } }

Updating data records for SCEL1_1_1_1_0_0_0/0 Updating data records for SCEL1_1_1_1_0_0_0/1 Updating data records for SCEL2_1_1_2_0_0_0/0 Updating data records for SCEL2_1_1_2_0_0_0/1 Updating data records for SCEL2_1_1_2_0_0_0/2 Updating data records for SCEL2_1_1_2_0_0_0/3 Updating data records for SCEL2_1_1_2_0_0_0/4 Updating data records for SCEL2_1_1_2_0_0_0/7 Updating data records for SCEL2_1_1_2_0_0_0/8 Updating data records for SCEL2_1_1_2_0_0_0/9 Updating data records for SCEL2_1_1_2_0_0_0/10 Updating data records for SCEL2_1_2_1_1_0_0/0 Updating data records for SCEL2_1_2_1_1_0_0/1 Updating data records for SCEL2_1_2_1_1_0_0/3 Updating data records for SCEL2_1_2_1_1_0_0/5 Updating data records for SCEL2_1_2_1_1_0_0/6 Updating data records for SCEL2_1_2_1_1_0_0/7 Updating data records for SCEL2_1_2_1_1_0_0/8 Updating data records for SCEL2_1_2_1_1_0_0/10 Updating data records for SCEL2_2_1_1_0_1_1/0 Updating data records for SCEL2_2_1_1_0_1_1/2 Updating data records for SCEL2_2_1_1_0_1_1/3 WARNING: Could not map 22 results. See detailed report: "......./reports/update_report.4/update_config_fail"

[MJJHKU]

Dear Dr. Zhang

This has been a problem for me for a long time. Maybe due to the very large relaxations....In the tutorials, which says the conflicts could be resolved using either min-energy or min-deformation rule. Do you know some about this?

Best Jianjun

[sjtuzhanglei]

Hi Jianjun,

I don't know exactly what you mentioned here. Yours might be that one structure goes to another structure by relaxation, or one configuration goes to another configuration, making multiple conflicting configurations?

My case here might not be due to large relaxations. It just failed without any clues.

[MJJHKU]

Dear Dr. Zhang,

Maybe due to this problem, therefore it could not mapping back. And the mapping Warning is the same with yours.

[sjtuzhanglei]

Hi Brian,

Can you help out? I am not sure what is min-energy or min-deformation rule.

Thanks!

[bpuchala]

The min-energy or min-deformation metics allow breaking ties if >1 structures map to the same configuration, to decide which properties to use. In this case, no successful mapping is being made. There are probably large atomic displacements or lattice relaxations. Inspecting the final relaxed states of the DFT calculations is necessary to understand exactly why.

[sjtuzhanglei]

Thanks Brian,

Yeah just as you said, the relaxed state has large atomic displacement, and volume/shape distortions. I guess this makes mapping to the prototype difficult.

May I know the threshold of distortion/displacement that CASM or cluster expansion will fail?

In this case, the CE method is not a good option any more, right?

[bpuchala]

I'd like to improve the mapping error information when I can. I think the main ways that it fails now are (i) the min_va_frac / max_va_frac / max_vol_change / fix_lattice / fix_volume / ideal settings make it impossible to map the lattice (i.e. the lattice isn't actually ideal or within the max_vol_change parameter) or the atoms (i.e. va frac is very large), or (ii) there are large relaxations and multiple configurations that a structure can map to equally poorly. The update_config_fail file might have some information about that.

For the validity, it really depends on the problem at hand. For fitting and applying the CE, you need to understand what configurations are failing to map and what configuration space you intend to apply it for. Often there is a stable configuration space that corresponds to the material / phases you care about, but then outside of that the crystal structure is unstable and a different prim is necessary.