Potassium-activated anionic copper and covalent Cu-Cu bonding in compressed K-Cu compounds

Area of Science:

• Materials Science
• Solid State Chemistry
• Computational Materials Science

Background:

• Elemental copper and potassium are immiscible under ambient conditions.
• Pressure is a known factor that can alter electronic structures and promote reactions between elements.

Purpose of the Study:

• To predict the formation of novel potassium-copper (K-Cu) compounds under pressure.
• To investigate the structural and electronic properties of these predicted K-Cu phases.

Main Methods:

• Unbiased structure search using first-principles calculations.
• Analysis of electronic structure and simulated X-ray diffraction patterns.

Main Results:

• Four new K-Cu compounds (K3Cu2, K2Cu, K5Cu2, K3Cu) were predicted under moderate pressure.
• Predicted structures exhibit diverse copper aggregations (dimers, chains, polyhedrons).
• Simulated X-ray diffraction of K3Cu2 matches a previously synthesized compound.

Conclusions:

• Potassium-copper compounds can form under pressure, exhibiting novel structural and electronic characteristics.
• Copper atoms act as anions, accepting electrons from potassium, leading to covalent Cu-Cu interactions.
• Findings advance the understanding of phase diversity in alkali-metal and transition-metal systems.