To obtain an ITP (Include Topology Parameter) file and a PDB (Protein Data Bank) file for a boron nitride nanotube (BNNT) structure that you can use with the CHARMM36 force field, you have a few options:
You can generate the BNNT structure using a computational modeling program such as LAMMPS or GROMACS, and then save the structure in ITP and PDB format.
You can search online databases such as the Protein Data Bank (PDB) or the Materials Project for BNNT structures that have already been generated and are available for download. These structures may be provided in ITP and PDB format, or you may need to convert them using a tool such as Open Babel.
You can use a web-based tool such as Nano-HUB's BNNT Builder to generate a BNNT structure and download it in ITP and PDB format.
Regardless of which option you choose, it is important to carefully check the accuracy and quality of the BNNT structure before using it in your simulations. Incorrect or incomplete structures can lead to inaccurate or unreliable results.