Dynamically consistent method for mixed quantum-classical simulations: A semiclassical approach.

Area of Science:

• Quantum mechanics
• Computational chemistry
• Theoretical physics

Background:

• Accurate simulation of quantum real-time correlation functions is crucial for understanding molecular dynamics.
• Existing semiclassical (SC) approximations have limitations in capturing the full spectrum of quantum to classical behavior.
• Developing a unified framework that bridges quantum and classical dynamics remains a significant challenge.

Purpose of the Study:

• To introduce a novel semiclassical framework, the Mixed Quantum-Classical Initial Value Representation (MQC-IVR).
• To demonstrate the MQC-IVR's ability to reproduce established quantum-limit and classical-limit SC approximations.
• To provide a consistent dynamic framework for mixed quantum-classical simulations.

Main Methods:

• Development of the MQC-IVR by applying a modified Filinov transformation to a quantum-limit SC formulation.
• Association of a tunable Filinov parameter with each degree of freedom to control quantization.
• Numerical validation using model 1D and 2D systems for calculating real-time correlation functions.

Main Results:

• The MQC-IVR framework is shown to be tunable, interpolating between quantum and classical limits.
• The method successfully reproduces known quantum-limit and classical-limit semiclassical approximations.
• Numerical accuracy is demonstrated across the full range of quantum-to-classical behaviors in model systems.

Conclusions:

• The MQC-IVR provides a versatile and accurate approach for simulating quantum dynamics.
• This framework offers a consistent method for mixed quantum-classical simulations.
• The MQC-IVR advances the capability to model systems exhibiting a wide range of quantum effects.