Cu-Zr-Hf-Ti金属玻璃弹性模量遗传性的电子结构起源

Electronic Structure Origin of Elastic Modulus Inheritance in Cu-Zr-Hf-Ti Metallic Glasses

摘要:

金属玻璃的弹性模量通常被认为“遗传”于其溶剂组元（主组元），然而这一规律在Cu基金属玻璃体系中存在显著例外。为揭示此类反常遗传现象的物理机制，本研究选取Cu-Zr-Hf-Ti体系作为研究对象，基于第一性原理计算，系统开展了从宏观弹性模量、原子尺度键合特性到电子结构的多尺度分析。研究发现，该体系的弹性模量受控于以Zr-Zr和Zr-Ti键为代表的低刚度原子间相互作用的集体响应，而非主组元Cu。电子结构分析进一步证实，尽管Cu在成分上占主导地位，但费米能级附近的电子态密度主要由次要组元Zr和Hf的d轨道电子贡献。Hf的引入增强了Cu-3d与Hf-5d的轨道杂化，降低了费米能级附近的电子态密度，通过提升键合的方向性与共价性显著提高了刚度，同时体积模量与剪切模量比值（B/G）及泊松比（ν）数值的降低预示了韧性的潜在下降趋势。本研究证实，金属玻璃弹性模量的遗传性本质上取决于对费米能级附近电子态密度起主导作用的关键组元，这为从电子结构层面出发，理性设计具有特定力学性能的金属玻璃提供了理论依据。

Abstract:

The elastic modulus of metallic glasses (MGs) is commonly considered to be “inherited” from their solvent (principal) element. However, this rule exhibits significant exceptions in Cu-based MG systems. To uncover the physical mechanism behind this anomalous inheritance, this study selected the Cu-Zr-Hf-Ti system as the research object. Based on first-principles calculations, a multi-scale analysis was conducted, including the macroscopic elastic modulus, atomic-scale bonding characteristics, and the electronic structure. The results show that the elastic modulus of this system is governed by low-stiffness interatomic interactions represented by Zr-Zr and Zr-Ti bonds, rather than by the principal element Cu. Electronic structure analysis further confirms that, although Cu dominates in composition, the electronic density of states (DOS) near the Fermi level is primarily contributed by the d-orbitals of the minor elements Zr and Hf. The introduction of Hf enhances the orbital hybridization between Cu-3d and Hf-5d, and reduces DOS near the Fermi level, thereby significantly increasing stiffness by promoting the directionality and covalency of bonding. Concurrently, the decrease in ratio of bulk modulus to shear modulus (B/G) and Poisson's ratio (ν) values suggests a potential decline in toughness. This work clarifies that the inheritance of the elastic modulus in MGs is essentially determined by the key element that dominates the electronic DOS at the Fermi level. This finding provides a theoretical basis for the rational design of MGs with tailored mechanical properties from an electronic structure perspective.