Flexible Force Field Parameterization through Fitting on the Ab Initio-Derived Elastic Tensor.

Area of Science:

• Materials Science
• Computational Chemistry
• Solid-State Physics

Background:

• Developing accurate force fields for metal-organic frameworks (MOFs) is crucial for predicting their behavior.
• The metal-linker interface presents a significant challenge in MOF force field parameterization.
• Existing methods often struggle to capture the complex mechanical properties of MOFs.

Purpose of the Study:

• To propose and validate a novel, top-down approach for parameterizing flexible force fields for MOFs.
• To utilize ab initio density functional theory (DFT) calculations of the elastic tensor for parameter fitting.
• To demonstrate the effectiveness of this method by deriving a new flexible force field for MIL-47(V).

Main Methods:

• Ab initio density functional theory (DFT) calculations to obtain the elastic tensor.
• Fitting functional forms and force field parameters to the computed elastic tensor components.
• Derivation of a new flexible force field model for the specific MOF, MIL-47(V).

Main Results:

• Successfully derived a new flexible force field for MIL-47(V) using the proposed method.
• Observed negative thermal expansion in the MIL-47(V) model.
• Demonstrated that framework flexibility has minimal impact on adsorption and transport of small guest molecules.

Conclusions:

• The proposed method of fitting force field parameters to the elastic tensor is a robust approach for developing accurate flexible MOF models.
• This top-down strategy effectively captures the mechanical behavior of the entire periodic structure.
• The derived force field for MIL-47(V) provides a valuable tool for further research in MOF design and application.