Hello,

I am trying to define GaN wurtzite crystal in LAMMPS based on what was posted on the LAMMPS-users forum, which is:

```
> variable x equal 5.19294/3.18
>
> variable y universe 3.18
>
>
>
> lattice custom $y a1 0.5 -0.866025 0.0 a2 0.5 0.866025 0.0 a3 0.0
> 0.0 $x basis 0.33333333 0.66666667 0.1252 basis 0.66666667 0.33333333 0.625
> basis 0.33333333 0.66666667 0.5 basis 0.66666667 0.33333333 0.0
```

Q1: Considering the unit vectors, why we have 0.5 -0.866025 0.0 for a1 (i), 0.5 0.866025 0.0 for a2(j). And where do 0.5, -0.866025, and 0.866025 come from?

Q2: Shouldnâ€™t the unit vectors be defined as follows and not by numbers like 0.5 or -0.866025:

```
1 0 0
0 1 0
0 0 1
```

I appreciate your input.

Farzad