Zentropy-Based Insights into Short-Range Order and Mechanical Properties in High Entropy Alloys
PI: Shunli Shang (Materials Science and Engineering)
Tuition for graduate students will be covered by PI’s federal funding. The remainder of the researcher’s salary for postdoc and research faculty will be covered by PI’s federal funding.
Abstract: Disorder is a fundamental characteristic of materials, playing a critical role in determining their macroscopic functionalities. This project seeks to uncover the underlying physics governing short-range order (SRO) and to predict its influence on emergent properties in high-entropy alloys, with a focus on the VCoNi model system. We hypothesize that both SRO and its associated property trends can be accurately predicted using our Zentropy theory, a multiscale entropy framework. This project includes advancing theoretical understanding, fostering interdisciplinary collaboration with junior researchers, exploring novel scientific ideas, developing open-source computational tools, and creating preliminary results for gaining federal funding.
Introduction: Disorder is a pervasive feature in materials, arising from non-repeating variations in composition, magnetic arrangements, and other characters. However, even in materials commonly regarded as disordered, such as high- and medium-entropy alloys (HEAs and MEAs), short-range order (SRO) has been directly observed in systems like VCoNi [1] and NiCoCr [2]. These findings suggest that the degree of disorder (fDoD) is a critical parameter to regulate key material properties such as stacking fault energy, dislocation mobility, phase transformations, tensile strength, and yield behavior [3]. While, some studies argue that SRO has negligible or no measurable effect on yield strength [4], the role of fDoD remains a subject of active debate. Despite its importance, current methods for quantifying fDoD are largely phenomenological or incomplete [5], highlighting the need for a more rigorous and predictive framework. This motivates the present project to quantitatively predict fDoD and elucidate its impact on mechanical properties of complex alloys.
Approach: For a thermodynamic perspective, characterizing disorder hinges on accurately describing entropy, for example, DoD = conf/idea , by comparing actual and ideal configurational entropies [5]. However, a major challenge in calculating free energy of a system lies in its total entropy. To address this, we recently proposed the Zentropy theory to accurately predict entropy [6], stipulating that the total entropy of a system is the summation of Gibbs entropy among different configurations and the statistically averaged quantum entropies of those configurations, where the key inputs are free energy for each configuration predicted by density functional theory (DFT) based quasiharmonic approach [6]. Additionally, we also developed a Zentropy-based methodology for efficiently computing entropy in both solids and liquids from a single molecular dynamics trajectory [7]. Based on accurate entropy and a well-defined free energy landscape, we can calculate fDoD and predict emergent properties such as order-disorder phase transition, Curie temperature, negative thermal expansion, and mechanical properties [6].
Tasks: In this seed project, we aim to predict both chemical and magnetic ordering in the model alloy VCoNi using the Zentropy theory, and to investigate how these orders impact mechanical properties such as tensile and shear strengthen. Concurrently, we will develop a Python-based software, PyZentorpy, to support these calculations and facilitate broader applications. The project will involve the following key tasks:
• DFT-based calculations of free energy of each configuration in VCoNi
• Predictions of fDoD and its correlation with tensile and shear strength
• Developments of PyZentropy, a Python-based toolkit for entropy and free energy analysis
• Preparations of reports, papers, and funding proposals.
Deliverables:
• A manuscript submitted for publishing in peer-reviewed journal
• A proposal submitted for gaining federal funding
• Report on this project