Predicting elastic properties of β-HMX from first-principles calculations

Area of Science:

• Computational Materials Science
• Quantum Chemistry
• Solid-State Physics

Background:

• Predicting the mechanical properties of energetic materials is vital for safety and performance.
• Density functional theory (DFT) is a common method, but its accuracy for van der Waals interactions in molecular crystals can be limited.

Purpose of the Study:

• To evaluate the performance of van der Waals (vdW) functions in DFT calculations for predicting the elastic constants of beta-cyclotetramethylene tetranitramine (β-HMX).
• To identify the most accurate DFT functional and vdW correction for modeling the mechanical behavior of β-HMX.

Main Methods:

• Density functional theory (DFT) calculations were performed on β-HMX crystals.
• Various exchange-correlation functionals (PBE, revised PBE) were tested with environment-dependent C6 vdW corrections.
• Calculated elastic constants were compared with experimental stress-strain data.

Main Results:

• vdW corrections significantly enhance the accuracy of elastic constant predictions for β-HMX.
• The PBE functional combined with D3(0) vdW corrections (PBE-D3(0)) provided the most accurate elastic constants.
• PBE-D3(0) calculations closely matched experimental mechanical response data.

Conclusions:

• vdW corrections are essential for accurate DFT predictions of elastic properties in energetic molecular crystals like β-HMX.
• PBE-D3(0) is a reliable computational approach for determining the mechanical response of β-HMX.
• This study provides a validated computational method for designing and understanding energetic materials.