# Metallic Bond Induces Soft Phonon Mode and Anharmonicity in Heusler Alloy

## TL;DR

This study explains how metallic bonding in Heusler alloys causes phonon softening and anharmonicity, leading to martensitic transformations and functional properties.

## Contribution

The study identifies the role of metallic bonding in inducing anharmonicity and phonon softening in Heusler alloys.

## Key findings

- Long-range interactions from metallic bonding between Ni─Ni spin-down d-orbitals cause phonon softening.
- Anharmonicity is significantly influenced by these interactions, affecting martensitic transformations.
- The findings offer a new perspective for designing phase transition functional alloys.

## Abstract

The fruitful functional performances of metastable Heusler alloys originate from the martensitic transformation driven by the transverse acoustic soft phonon mode, regulated by anharmonicity. However, the origins of the soft mode and the anharmonicity in these alloys remain unclear. In this work, using ab‐initio calculations combined with self‐consistent phonon theory (SCPH) and compressed sensing techniques in machine learning, a link among chemical bonding, long‐range interaction, soft mode, and anharmonicity is established using Ni2MnGa as a model system. The long‐range interaction rooted in metallic bonding between spin‐down d‐orbitals of Ni─Ni induces phonon softening and significant anharmonicity. This finding offers new insights into the role of metallic bonding and long‐range interactions in martensitic transformation, providing a fresh perspective for the design and optimization of phase transition functional alloys.

The fruitful functional performances of metastable Heusler alloys originate from the martensitic transformation driven by the transverse acoustic soft phonon mode, regulated by anharmonicity. This study reveals that the long‐range interaction rooted in metallic bonding between spin‐down d‐orbitals of Ni─Ni induces phonon softening and significant anharmonicity, which provides a fresh perspective for the design and optimization of phase transition functional alloys.