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Properties d3 input BAND section erroneously generated #30
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How the workchain is run? What is the input |
A wrong
Note the coordinates are huge (and always the same). I attach two such |
Ok, I see it now. Can you please also give the CRYSTAL input that generates such fort.9 files? |
Yep, see attached. |
In fact this is a result of two bugs, both of which are connected to the lack of machine precision. The first bug is due to the fact that there is no way to correctly represent 1/3 as the floating point number. There are special points in Brillouin zone for hexagonal lattice with coordinates equal to 1/3; however, exact representation of the fraction is impossible in the FP arithmetic, and hence it's approximated using the fraction with large numerator and denominator, giving large shrink factors. Now I approximate the coordinate with the fraction with the smallest denominator; this should do it. |
However, there is one more bug due to limited precision of writing geometry to fort.9. Because of that, cell vectors that are read from fort.9 are not the same as in fort.34, and hence, the angles between vectors are incorrect and the information about symmetry is lost. To solve the problem it seems necessary to pass the correct structure (i.e. the one from fort.34) to |
Even in this case there will be a problem with fort.25 parser, as it relies upon the struvture from fort.9 to populate |
@ansobolev is this related? SPECIAL_K collection contains no A for the orthorhombic lattice:
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Similar: |
There are no such special k-points as A and C in CRYSTAL manual, see Tables 13.1 and 13.2 therein. |
How did they appear then? The structures are indeed orthorhombic. Inconsistency between |
That's a |
Should I report to https://github.com/giovannipizzi/seekpath/issues? |
Please, could you update the SPECIAL_K with the new coordinates? |
Can you give the example of structure that leads to such points generation? Here there are many points listed; A and C are there, their coordinates depend on some alpha. That means that it's not possible to add the points to SPECIAL_K directly, their coordinates will depend on structure, and some post-processing should be done on them. |
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Unfortunately, the bug still persists:
The optimization producing the |
That's not a bug but rather unconventional way of introducing fractional coordinates implemented in CRYSTAL. They put coordinates as ordinary fractions, with shrinking factor as denominator (eg, 186200/372400). As long as symmetries are common, the coordinates of high symmetry points are represented as small fractions. In crystals with not so common symmetry high symmetry points can have irrational coordinates. They cannot be represented with ordinary fractions. |
Relatively often the strange huge values are generated, e.g.:
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