For example, this is an example with ibrav=4
```
crystal axes: (cart. coord. in units of alat)
a(1) = ( 1.000000 0.000000 0.000000 )
a(2) = ( -0.500000 0.866025 0.000000 )
a(3) = ( 0.000000 0.000000 1.633000 )
``` To understand what it means you need to check QE documentation and you will see that the lattice vectors are defined as: v1 = a(1,0,0), v2 = a(-1/2,sqrt(3)/2,0), v3 = a(0,0,c/a)