Sorry for not replying to this sooner. In principle it is rather easy using the Builder in 12.2, at least for narrow wires.
For instance, for a 100 Si nanowire:
- Open the Builder, then go to Add>Add From Database. Locate "silicon", then click "+" to add it to the stash.
- Use the plugin "Builders>Surface (Cleave)", specify Miller indices 1,0,0, then click Next>Next>Finish.
- Repeat the structure in the A/B plane, using "Bulk Tools>Repeat". Perhaps 5x5 is a good size.
- Now add vacuum around the wire, via "Bulk Tools>Lattice Parameters". Enter, say, 30 for A and B.
- Center the system, using "Coordinate Tools>Center".
- Passivate, using the passivation button on the left-hand toolbar.
- You're done!
This gives only one period in Z; if you want defects of other things you will need to repeat it in C also and make the relevant changes.
For 110 the same recipe applies directly.
For 111, there is one additional trick, since the primitive surface cell is hexagonal. To make an orthorhombic surface cell, set v1=u1+u2 and v2=u1+2*u2 on the second page of the Cleaver tool. Then, if you want a square wire, repeat twice as much in A as in B.
You can also make a circular shape by making a very large repetition at first, and then cut out a circle using the "circle" select tool. This selects the atoms inside
the circle, but if you press Ctrl+I (invert selection), then you can delete the atoms outside