# Phonon transmission in a mass-spring system

Dear LAMMPS users,

I am looking to investigate the transmission of phonons and was looking to do this using LAMMPS (which I have never used before). If it helps at all, right now I’m using Debian 8, and the version of LAMMPS I have is: 16 Feb 16.

I am studying the transmission of phonons from one solid to another while crossing a vacuum gap via Van der Waals forces - the way I am doing this in practice is by first considering each solid to be a ( initially, 1D) chain of springs with some atomic mass and spring constant. In between these solids is another spring, with a different spring constant. What I want to do is set off a wave (with unit amplitude, for instance) in one solid and have it propagate, go across the ‘interface’ spring, and then into the second solid and thus find what the amplitude is in the second solid, allowing me to recover a transmission coefficient. I have attached an image, included below, from the following paper (page 2) by Ezzahri and Joulain, which shows, schematically, what I mean to simulate: https://doi.org/10.1103/PhysRevB.90.115433.

Could anyone let me know if there is any reference material that would help me understand how to translate what I’ve said above into code/input script? The friendlier it is to beginners, the better!

Any help would be appreciated!

Many Thanks,

Ashim Sen Gupta

Imperial College London

Dear LAMMPS users,

I am looking to investigate the transmission of phonons and was looking to
do this using LAMMPS (which I have never used before). If it helps at all,
right now I'm using Debian 8, and the version of LAMMPS I have is: 16 Feb
16.

I am studying the transmission of phonons from one solid to another while
crossing a vacuum gap via Van der Waals forces - the way I am doing this in
practice is by first considering each solid to be a ( initially, 1D) chain
of springs with some atomic mass and spring constant. In between these
solids is another spring, with a different spring constant. What I want to
do is set off a wave (with unit amplitude, for instance) in one solid and
have it propagate, go across the 'interface' spring, and then into the
second solid and thus find what the amplitude is in the second solid,
allowing me to recover a transmission coefficient. I have attached an
image, included below, from the following paper (page 2) by Ezzahri and
Joulain, which shows, schematically, what I mean to simulate:
https://doi.org/10.1103/PhysRevB.90.115433.

Could anyone let me know if there is any reference material that would
help me understand how to translate what I've said above into code/input
script? The friendlier it is to beginners, the better!

​LAMMPS comes with a very thick manual, it doesn't come with personal
consulting and advising. people here on this mailing list are happy to
answer specific questions to specific details and commands of the LAMMPS
software, but nobody here has the time to devise a complete simulation
setup for you and give you a customized personal tutorial.​

​axel.​