Variables frequently used in C-API are explained. In interfaces of
other languages, the definition may be different, e.g., `lattice`

for Python interface is transposed.

`lattice`

¶**Attention**: In Python interface, `lattice`

is transposed
(Crystal structure (cell).)

Basis vectors (in Cartesian)

```
[ [ a_x, b_x, c_x ],
[ a_y, b_y, c_y ],
[ a_z, b_z, c_z ] ]
```

Cartesian position is obtained by

where is the basis vectors defined above and is , and is the atomic position in fractional coordinates given below.

`position`

¶Atomic points (in fractional coordinates with respect to basis vectors)

```
[ [ x1_a, x1_b, x1_c ],
[ x2_a, x2_b, x2_c ],
[ x3_a, x3_b, x3_c ],
... ]
```

`types`

¶Atomic species are differenciated by integers. The nubmers are just used to distinguishes atoms, and is not releated to atomic numbers.

```
[ type_1, type_2, type_3, ... ]
```

The number of elements is same as the number of atoms.

`rotation`

¶Rotation matricies (ingeger) of symmetry operations.

```
[ [ r_aa, r_ab, r_ac ],
[ r_ba, r_bb, r_bc ],
[ r_ca, r_cb, r_cc ] ]
```

`translation`

¶Translation vectors corresponding to symmetry operations in fractional coordinates.

```
[ t_a, t_b, t_c ]
```

`symprec`

¶Tolerance of distance between atomic positions and between lengths of
lattice vectors to be tolerated in the symmetry finding. The angle
distortion between lattice vectors is converted to a length and
compared with this distance tolerance. If the explicit angle tolerance
is expected, see `angle_tolerance`

.

`angle_tolerance`

¶**Experimental**

Tolerance of angle between lattice vectors in degrees to be tolerated in the symmetry finding. To use angle tolerance, another set of functions are prepared as follows

```
spgat_get_dataset
spgat_get_symmetry
spgat_get_symmetry_with_collinear_spin
spgat_get_multiplicity
spgat_find_primitive
spgat_get_international
spgat_get_schoenflies
spgat_refine_cell
```

These functions are called by the same way with an additional argument
of `const double angle_tolerance`

in degrees. By specifying a negative
value, the behavior becomes the same as usual functions. The default
value of `angle_tolerance`

is a negative value.