Quantum mechanics

Perturbation theory (quantum mechanics)

Dynamics (music)

Perturbation (astronomy)

Computer science

Acoustics

Classical mechanics

Observable

Statistical physics

Langevin dynamics

Thermodynamics

Physics

Quantum dynamics

Thermostat

Path (computing)

Quantum

Programming language

Langevin equation

Path integral formulation

The Journal of Chemical Physics

The properties of molecules and materials containing light nuclei are affected by their quantum mechanical nature. Modelling these quantum nuclear effects accurately requires computationally demanding path integral techniques. Considerable success has been achieved in reducing the cost of such simulations by using generalized Langevin dynamics to induce frequency-dependent fluctuations. Path integral generalized Langevin equation methods, however, have this far been limited to the study of static, thermodynamic properties due to the large perturbation to the system's dynamics induced by the aggressive thermostatting. Here we introduce a post-processing scheme, based on analytical estimates of the dynamical perturbation induced by the generalized Langevin dynamics, that makes it possible to recover meaningful time correlation properties from a thermostatted trajectory. We show that this approach yields spectroscopic observables for model and realistic systems which have an accuracy comparable to much more demanding approximate quantum dynamics techniques based on full path integral simulations.

Inexpensive modeling of quantum dynamics using path integral generalized Langevin equation thermostats