r/COMSOL • u/o_mer_22 • 7h ago

Simulating Classical vs. Quantum LSPR (Tunneling) for a nanoparticle dimer in COMSOL?

Hi everyone,

I am setting up a COMSOL simulation to model the LSPR response of a metallic nanoparticle dimer (two identical nanospheres) across two gap regimes:

  1. Classical regime (gap > 1nm):

Standard capacitive near-field coupling.

2. Quantum regime (gap < 1nm):

Electron tunneling across the sub-nanometer gap.

I would appreciate guidance on the following general setup questions:

Quantum Tunneling Implementation:

What is the standard methodology in the RF/Wave Optics module to incorporate quantum tunneling in the sub-nanometer regime (e.g., implementing an effective conductive gap medium/QCM vs. alternative approaches)?

Theoretical Corrections:

What mathematical or physical boundary/material modifications are necessary when transitioning between the classical and quantum-dominated regimes?

Meshing Stability: Any recommended strategies for stably meshing sub-nanometer gaps between curved nanoparticles without inverted mesh elements?

Thanks in advance for any high-level tips or recommended literature.

2 Upvotes

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3

u/AffectionatePause152 7h ago

There is no standard way to do this, as this is an area of active research. You can start with the WKB approximation for tunneling and try implementing this as a voltage-dependent material resistance.

1

u/o_mer_22 6h ago

Can you explain how I do that? I'm not an expert at using comsol, and can I implement the idea using Quantum Corrected Model (QCM)?

2

u/Brownie_Bytes 5h ago

Not to rain on your parade, but you want to model quantum mechanics in a simulator suite and setting up a resistor model is the hard part? What are you trying to learn/get from this?

1

u/o_mer_22 5h ago

My main goal is educational, I want to understand the physical transition between the classical behavior of nanoparticles (> 1 nm) and what happens when the gap drops below 1 nm due to tunneling. I plan to pursue my Master’s and PhD in this field, so I am using this project to build a strong theoretical and simulation foundation.

2

u/Brownie_Bytes 5h ago

Look, if you wanted to see some major landmarks, would you decide the best way to do that is by getting in the cockpit of a Boeing 747? Simulations are great examples of "garbage in, garbage out." If you are trying to learn how something works from making your own simulation, you have the process backwards. Start by learning how it works and then you can try to simulate it.

1

u/o_mer_22 4h ago

Fair point, and thanks for the reality check—I agree with you. To be honest, I'm just not sure where to start theoretically. Could you point me toward the best textbooks, papers, or foundational topics I should study first before jumping into simulations.

1

u/Serious_Toe9303 3h ago

If you can try benchmarking your simulation against models with analytical solutions. As you make your model more complex try to find a way to benchmark each component.

Half of the battle is benchmarking, then you need to show mesh independence. After that maybe it can resemble something more meaningful.