La4.27Mg2.89Zn30, a new structure type with strong positional disorder

Area of Science:

• Solid-state chemistry
• Crystallography
• Materials science

Background:

• The study of intermetallic compounds is crucial for developing new materials with tailored properties.
• Understanding complex crystal structures provides fundamental insights into chemical bonding and atomic arrangements.
• Existing structure types like hexagonal CaCu(5) and Th(2)Ni(17) serve as foundational models for new structural discoveries.

Purpose of the Study:

• To characterize a newly discovered ternary intermetallic compound, La(4.27)Mg(2.89)Zn(30).
• To determine the crystal structure and atomic coordination within this new phase.
• To explore its relationship with known hexagonal structure types.

Main Methods:

• Single-crystal X-ray diffraction was used to determine the crystal structure.
• Analysis of atomic arrangements and coordination polyhedra was performed.
• Comparison with related hexagonal structure types (CaCu(5), Th(2)Ni(17)) was conducted.

Main Results:

• A new structure type for La(4.27)Mg(2.89)Zn(30) was identified.
• The structure is derived from CaCu(5) and Th(2)Ni(17) types through deformation and substitution.
• Distinct coordination polyhedra were observed for La, Mg, and Zn atoms, with Zn exhibiting icosahedral coordination.
• Positional disorder was noted due to Mg substitution for La.

Conclusions:

• The new ternary phase represents a unique addition to the family of hexagonal intermetallic structures.
• The observed coordination and disorder provide insights into the stability and formation of complex alloys.
• This discovery expands the known structural diversity in lanthanum-magnesium-zinc systems.