The proper use of npt, nvt or nve when deform bulk materials in uniaxial tension

Dear all users:
In LAMMPS website, some tutorials are presented in LAMMPS tutorials page (https://icme.hpc.msstate.edu/mediawiki/index.php/LAMMPS_tutorials). The LAMMPS Beginner Help 3 shows how to deform a three-dimensional periodic simulation cell in uniaxial tension for aluminum and the simulation was performed in the NPT ensemble. however, the LAMMPS Beginner Help 9 shows how to deform a nanowire but the simulation was performed in the NVT ensemble, I read the related commands about fix npt and nvt , and did not find the reason that why they used different ensemble. Actually they both used periodic conditions in three dimensions, and similar pair_style of metal atoms. Are their real loading condition different? can someone give me some advice? thanks very much!
best wishes!

that’s not really a LAMMPS Q - it’s an MD or stat mech

question. There is no fundamental reason to prefer NPT
over NVT - it just depends on what you want to equilibrate.

Steve

Dear Steve:
Thank you for your help!

Xuepeng Liu