Structural and electronic properties of KY(BH₄)₄: DFT+U study

Area of Science:

• Materials Science
• Computational Chemistry
• Solid-State Chemistry

Background:

• Mixed-cation borohydrides are crucial for energy applications.
• Standard Density Functional Theory (DFT) methods inaccurately predict electronic structures and band gaps.
• Accurate theoretical models are needed for mixed-cation borohydrides.

Purpose of the Study:

• To systematically investigate the structural and electronic properties of KY(BH4)4.
• To evaluate the performance of DFT+U methods for this material.
• To determine the most suitable DFT+U approach for KY(BH4)4.

Main Methods:

• First-principles calculations using Density Functional Theory with the Hubbard U correction (DFT+U).
• Comparison of LDA+U, PBE+U, and PW91+U methods.
• Analysis of lattice volume, total energy, and electronic structure.

Main Results:

• LDA+U significantly underestimated the lattice volume.
• PBE+U and PW91+U methods showed good agreement with experimental data at specific U values.
• PW91+U with U=4 yielded lower total energy, suggesting its suitability.

Conclusions:

• The PW91+U method is recommended for accurate studies of KY(BH4)4 structural and electronic properties.
• Electrostatic interactions dominate between K+ and BH4-, with weak covalent bonding between Y3+ and BH4-.
• This work provides a reliable theoretical foundation for mixed-cation borohydride research.