Investigate classical phonon occupations for INS simulations

[ajjackson]

Describe the outcome that is desired. In simulation of inelastic neutron scattering, there are several levels of theory that can be applied which capture different levels of quantum effects:

• classical molecular dynamics neglects nuclear quantum effects and zero-point motions
• quantum-harmonic-oscillator description includes zero-point motions but not quantum confinement effects or longer-range excursions
• path-integral molecular dynamics includes nuclear quantum effects and can account for e.g. quantum confinement, tunneling

Abins operates at the second of these levels. In order to facilitate comparison with classical simulations and quantify significance of zero-point motions it would be interesting to substitute the Bose occupation factors with a simpler classical harmonic oscillator model.

Does the outcome relate directly to a problem? Please describe. Multiple collaborators, internal and external, have expressed an interest in this. Most INS measurements are taken at low temperature and most molecular dynamics is performed with classical ensembles.

Describe any solutions you are considering

I need to re-read some textbooks and papers to determine how easy/safe this is. Even if we have classical motions, the neutron scattering itself remains quantum in nature....

Additional context

[github-actions[bot]]

This issue has been automatically marked as stale because it has not had activity in 6 months. It will be closed in 7 days if no further activity occurs. Allowing issues to close as stale helps us filter out issues which can wait for future development time. All issues closed by stale bot act like normal issues; they can be searched for, commented on or reopened at any point. If you'd like a closed stale issue to be considered, feel free to either re-open the issue directly or contact a developer. To extend the lifetime of an issue please comment below, it helps us see that this is still affecting you and you want it fixed in the near-future. Extending the lifetime of an issue may cause the development team to prioritise it over other issues, which may be closed as stale instead.

[github-actions[bot]]

This issue has been closed automatically. If this still affects you please re-open this issue with a comment or contact us so we can look into resolving it.