Comparative study of density functionals for the description of lithium-graphite intercalation compounds.

Area of Science:

• Computational materials science
• Condensed matter physics
• Quantum chemistry

Background:

• Conventional density functional theory (DFT) methods struggle to accurately describe van der Waals (vdW) interactions in layered materials like graphite.
• Accurate modeling of vdW forces is crucial for understanding the properties of graphite intercalation compounds (GICs).

Purpose of the Study:

• To compare the performance of semiempirical dispersion corrections (e.g., Grimme) and nonlocal vdW functionals for describing graphite and lithium-GICs (Li-GICs).
• To evaluate the accuracy of these methods in predicting geometric structure, thermodynamic stability, and lithium-graphite intercalation potential.

Main Methods:

• Density functional theory (DFT) calculations.
• Application of PBE-D3(BJ) dispersion correction.
• Utilization of nonlocal vdW functionals (optB88-vdW, optB86b-vdW, revPBE-vdW).
• Computation of formation energies and intercalation potentials for Li-GICs.

Main Results:

• PBE-D3(BJ) accurately reproduces graphite lattice parameters and interlayer binding energy but underestimates Li-GIC stability.
• Nonlocal vdW functionals (optB88-vdW, optB86b-vdW, revPBE-vdW) show good agreement for Li-GIC stability but overestimate vdW interactions in graphite.
• Only the revPBE-vdW functional qualitatively reproduces the experimental step-function behavior of the Li-graphite intercalation potential.

Conclusions:

• The choice of DFT method significantly impacts the accuracy of predicting properties of Li-GICs.
• revPBE-vdW emerges as a promising functional for describing the complex interactions and intercalation behavior in Li-GICs.
• Further development of vdW functionals is needed for comprehensive modeling of layered materials.