Unveiling Superior Fracture Toughness in MnCoSb Half-Heusler Alloy: A First-Principles Guide for Designing...

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Chemistry

Background:

• Half-Heusler (HH) alloys are promising for spintronics and magnetism.
• Understanding their mechanical properties, especially fracture toughness, is crucial for applications.
• First-principles calculations offer a reliable method for predicting material behavior.

Purpose of the Study:

• To comprehensively investigate the stability, electronic, structural, and mechanical properties of MnCoSb, MnCoAs, MnCoP, and MnNiSb alloys.
• To determine the fracture toughness and identify alloys with superior mechanical performance and damage tolerance.
• To establish relationships between microscopic and mechanical properties for HH alloys.

Main Methods:

• Density Functional Theory (DFT) based first-principles calculations were employed.
• Phonon spectra, formation energies, and Born criteria were used to assess stability.
• Mechanical properties (Young's, bulk, shear moduli) and fracture toughness (K_IC) were calculated.

Main Results:

• All four HH alloys exhibit half-metallic characteristics with a band gap in the spin-down channel.
• Phonon spectra and negative formation energies confirm dynamic and thermodynamic stability.
• MnCoSb shows the best mechanical performance and damage tolerance (K_IC up to 2.63 MPa·m^1/2), while MnCoP is more brittle.

Conclusions:

• The investigated HH alloys possess desirable stability and half-metallic properties.
• MnCoSb demonstrates excellent fracture toughness and mechanical reliability, suitable for demanding applications.
• This research provides a theoretical basis for developing damage-tolerant HH alloys in spintronics and magnetism.