Cluster Formation in the Superconducting Complex Intermetallic Compound Be₂₁Pt₅.

Area of Science:

• Materials Science
• Solid State Chemistry
• Crystallography

Background:

• γ-brass type materials (Cu5Zn8 type) are common intermetallic compounds.
• Hume-Rothery's valence electron concentration approach is often used for their electronic interpretation.
• γ-brass type phases involving main-group elements are rare.

Purpose of the Study:

• To synthesize and characterize the novel intermetallic compound Be21Pt5.
• To elucidate its crystal structure, chemical bonding, and physical properties.
• To investigate its potential as a complex metallic alloy (CMA) and its superconducting behavior.

Main Methods:

• Synthesis of Be21Pt5.
• Crystal structure solution using synchrotron and neutron powder diffraction data.
• Analysis of chemical bonding via the electron localizability approach (ELI-D).
• Characterization of physical properties, including magnetic susceptibility and superconductivity.

Main Results:

• Be21Pt5 crystallizes in the cubic space group F4̅3m with 416 atoms per unit cell.
• The structure is a superstructure of the γ-brass type, featuring nested polyhedral units (clusters).
• Novel bonding types, including multicenter and cluster bonds (8-14 atoms), were identified.
• Be21Pt5 is a diamagnetic metal exhibiting superconductivity with a critical temperature (Tc) of 2.06 K.

Conclusions:

• Be21Pt5 represents a new member of the γ-brass type intermetallic compounds and complex metallic alloys.
• Its complex structure and bonding are consistent with the electron localizability approach.
• The discovery of superconductivity in this rare CMA highlights its unique electronic and structural characteristics.