How to delete atoms outside of a defined region

LAMMPS LAMMPS Beginners
1

Hello everyone!
I am trying to generate a nanorod structure of nitinol using a cif file.

Here is the relevant part of my code:

Read the LAMMPS data file converted from the CIF file

read_data nitinol.data

Replicate the unit cell to create a larger structure

replicate 20 20 50 # Adjust replication factors for the desired nanorod length

Define a cylindrical region to create the nanorod

region nanorod cylinder z 29.8806613 29.8806613 10.0 INF INF # Cylinder with radius of 10 units along z-axis

Delete atoms outside the cylindrical region to form the nanorod

delete_atoms region nanorod

But the delete_atoms command here removes the atoms inside the nanorod and creates a cylindrical hole inside the simulation box.
How can I remove the atoms that are outside the region nanorod?

2

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Define a suitable region that describes the outside instead of the inside of the given cylinder. Details are in the documentation.