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## Option: duplicate

#### Syntax

`-duplicate <Nx> <Ny> <Nz>`

#### Description

This option allows to duplicate a system in the three directions of space. It can be useful for (but not restricted to) building a supercell from a unit cell.

The translational vectors used to repeat the system are the base vectors of the original cell, noted `Hx`, `Hy` and `Hz`. The command-line parameters must be integers and, if they need any explanation at all:

- Nx: number of times the system is repeated along the first box vector `Hx`.
- Ny: number of times the system is repeated along the second box vector `Hy`.
- Nz: number of times the system is repeated along the third box vector `Hz`.

If all values are equal to 1 then the system remains the same (since it is multiplied one time along all directions). Any value equal to 0 is automatically replaced by 1, as a zero dimension would wipe out the whole system. If a negative value is provided, then the system is mirrored along that axis, and then expanded in the direction of negative coordinates.

The replicas of the original system are appened to the original system. To change the order of atoms one can use the option `-sort`.

If original atoms possess auxiliary properties, the duplicate atoms have the same auxiliary properties.

If a selection was defined (with the option `-select`) then only selected atoms are duplicated. After the duplication, the selection will remain the same (i.e. the duplicates of selected atoms will not be selected).

#### Default

By default the system is not duplicated.

#### Examples

- `atomsk unitcell.cfg -duplicate 2 2 4 supercell.xyz`

  This will create a 2x2x4 supercell from `unitcell.cfg`, and output it to `supercell.xyz`.

- `atomsk initial.xyz -dup 6 4 0 final.cfg`

  This will duplicate the system six times along X, four times along Y, and one time along Z. Note that the "0" along the Z direction has the same meaning as "1", i.e. the system is not duplicated but still appears once along that direction.

- `atomsk initial.cfg -dup -3 1 1 final.cfg`

  The system will be duplicated -3 times along X, i.e. it will be mirrored along the X direction, and then copied 3 times in the direction of negative X coordinates.

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