Dear all,

Hope you all have a good time.

While performing simulations on MOF-303 to study its gas adsorption properties, I encountered some issues regarding forcefield parameters and would like to seek your professional advice.

In previous simulation tasks, the COMPASS forcefield has consistently demonstrated high reliability and accuracy. However, during the current simulation of MOF-303, I found that the lack of specific Aluminum (Al) parameters in the library is causing significant structural distortions during geometry optimization.

I would like to inquire about the following points:

1. Forcefield Roadmap: Are there any official plans to add more comprehensive MOF-specific atom types or parameters (specifically for metal centers like Al) to the COMPASS III library in the near future?
2. Dreiding FF & Inversion Parameters: As an alternative, I attempted to use the Dreiding forcefield but found that it lacks inversion parameters for the following clusters: O-Al-Al-H and O-Al-H-Al.

Given the objective is to evaluate gas adsorption performance:

• Would it be acceptable to perform these simulations (such as GCMC or fixed-pore MD) using a rigid framework (fixing the MOF coordinates to DFT-optimized positions)?
• Or is it considered essential to manually verify and implement these missing inversion parameters to ensure a flexible framework simulation?

I would appreciate your insight on whether a rigid framework is a standard acceptable practice for this specific 1D-chain Al-MOF system, or if flexibility is crucial for accurate adsorption results.

Thank you for your time and assistance.

Best regards,

Rakhoon Choi