[Spglib-users] Tolerances differ in get_int and get_sym?

[Michael R. <mjr...@gm...>]

I am, in general, very impressed with spglib. It does a difficult and
tedious task well.

However, one point confuses me. It seems that the symmetry operations
returned by spg_get_symmetry are not always consistent with the
international symbol found by spg_get_international when the same
tolerance is used for both. The attached example prints

Symprec=1e-05, int symbol is Cmc2_1
Symprec=2e-05, int symbol is Cmc2_1
Symprec=0.0001, int symbol is Cmc2_1

Symprec=1e-05, 4 symmetry operations
Symprec=2e-05, 4 symmetry operations
Symprec=0.0001, 8 symmetry operations

whereas I would expect Cmc2_1 to have 8 symmetry operations always.

Am I confused, or is this a slight bug in spglib? (I am using version
1.3 from Sourceforge.)

Regards,

Michael